zap's mental ray tips

Montreal Trip

2011-10-16T10:46:00.001+02:00

Popping over to Montreal for a while to meet my new collegues...

Oh and if someone thought this blog was dead now - think again ;)

/Z

This is the 100:th post...

2011-09-28T17:30:00.001+02:00

...and it's only appropriate that it is about the fact that I've been hired by Autodesk.

Yes, you've seen Ken spill the beans over on CGTalk. It is true. Autodesk has hired me to handle rendering and funky stuff like that. Pixels. Whatnot. Friday sept 30:th is my last day at mental images/NVidia (which I end by doing the meet-and-greet-3d event in Berlin, see previous post), and Monday October 3:rd my first day at at Autodesk... this time around (I used to work for Autodesk in the past, doing mechanical design software).

This all started around some discussion between my good friends Neil Hazzard, Shane Griffith and myself back at EUE (all good friends which will now be my actual colleagues). It was thrown out as an idea, we pondered the thought, thought it made sense, and I talked to my managers at mental images/NVidia, and everybody thought it made a lot of sense.

Integration of mental ray and iray into Autodesk products have always been.. problematic. Integration work was done by Autodesk, but there was never a dedicated person with enough precise know-how of the nitty-gritty details to handle it (or sometimes simply not enough priority put on it). Well...... now I will be working there. 'nuff said :)

I think this will be interesting, and I've been "Shader Wizard" for mental images (now "NVidia ARC" - "Advanced Rendering Center") for 7+ years now, perhaps it's time to move forward to New Challenges. Todays physical rendering doesn't really require "shaders" in the same way it did in the past anyway..... 'tis all BSDF's and physics and shiny stuff :)

It's not like I'm moving far anyway. I will probably be in all the same meeting, just on the other "side"....

I think this will be really interesting, and the future is Bright (about 95000 cd/m^2 to be exact). Lets go there together.

With Sunglasses.

Also, as I type this I am finalizing some Really Cool Sh%t. Stay tuned - as always :)

/Z

Appearing at Meet and Greet 3D

2011-09-14T14:58:00.001+02:00

On Sepmber 30:th 2011 I will be speaking at the Meet and Greet 3D event in Berlin.

I will do a small sit-down session about Linear Workflow at 2 PM, and a big-hall presentation about the physics of light at 11.50AM. <=== UPDATED TIME!!!

Venue info etc. available at www.MeetAndGreet3D.com

Location:

Forum Adlershof, Rudower Chaussee 17, 12489 Berlin

See you all there. :)

/Z

User Survey (and a chance to Win a Quadro 6000!)

2011-08-23T16:16:00.001+02:00

Just a quick note; We are currently running a user survey, and anyone who fills this in can win a NVIDIA Quadro 6000 graphics card!

It's a survey about how you use mental ray, and we want to gauge how it is being used across all possible industries. Appreciate your answers!

So please take the survey by clicking right here!

/Z

What if SIGGRAPH was held in a Pub?

2011-06-29T10:34:00.010+02:00

Have you ever wondered what it would be like if SIGGRAPH was about 200 of your best friends, had all the cool talks but none of the showfloor commercial glitz... and was held in a pub?

If you think that sounds like a good idea, you should have registered for the End User Event (see previous post). Me? I'm packing my last thing, flying down there now.

If you wish you were there, well..... I told you already. In the aformentioned previous post :)

This year I'm going a bit more abstract than previous years, and will be talking about "the Physics of Light", and 'tis gonna be fun.

I will (connection willing) try to amend this post with some pictures, videos, and other stuff as the event happens.

For those who want the (likely) stream of crazy updates, tune in to my twitter at twitter.com/MasterZap.... connection willing, of course.

/Z

Welcome to EUE 2011

2011-05-18T08:09:00.001+02:00

As several years previously, I will be presenting at the EUE (= "End User Event") 2011 in Utrecht, Netherlands.

The event is June 30:th/July 1:st, and it is held in the Florin, a nice old building that used to be a bank, but now is a pub..... with adjoined conference rooms.

Think of the event as the worlds smallest SIGGRAPH - only with the commercial glitz shaved off, and held in a pub. And if you walk outside, you are not run over by yellow cabs, but by blonde students on bicycles. Seriously, you almost need a bicycle helmet to walk the streets here. :)

Check out the www.EndUserEvent.com site for more details; there is even a Youtube behind-the-scenes channel where you can see the organizers setting up the event, which I found neat.

This year I will be talking about light, the perception thereof, and how to translate that knowledge to what you do in CG.

But I'm not the only one rambling, other speakers include:

Jeff Mottle (CG Architect)
Wayne Robson (y'know mudbox guy)
Rune Spaans (about his work on Troll Hunter)
Jamie Gwilliam (Autodesk)
Neil Hazzard (Autodesk)
Shane Griffith (Autodesk, will be holding an NDA session on future dev. of 3ds Max)
Ted Boardman (often mistaken for a member of ZZ top)
Johan Boekhoven
Eric de Broche
Yoni Cohen
Borislab "Bobo" Petrov
Hristo Velev
...and many more, see here

While waiting, what about the trailer for Troll Hunter that Rune worked on? Think of it as "Cloverfield goes to Norway. With Trolls". :)
See you in Utrecht!

/Z

Render Optimizer script for max 2012

2011-04-26T10:16:00.004+02:00

I discussed progressive sampling in the previous post. Thorsten Hartmann and Artur Leão has collaborated on an "Über-script" for handling a ton of stuff. Torsten calls his variant "Render Optimizer" and can be found on this link:

http://www.infinity-vision.de/blog/render_optimizer

The Render Optimizer does a lot more than just turn on unified sampling, and Thorsten has several tutorial on the various subcomponents.

If you are overwhelmed by the number of tabs on Thorstens version, Artur also independently has a slightly different version on his site, called "mr Options Manager", which you can find here:

http://dimensao3.com/al/

I will be updating this post w. some tricks-and-tips myself shortly.
For now, Enjoy Thorsten and Arturs cool work!

/Z

2012 and Unified Sampling

2011-04-15T11:39:00.001+02:00

Hello World!

The new 2012 versions of the Autodesk products Max/Maya/Softimage are upon us, and they are loaded up with mental ray 3.9.

One of the cool new features in 3.9, which doesn't seem to be exposed in some of the products, is "unified sampling".

The new "Unified Sampling" is a new way to choose which and how many samples (i.e. "rays") are shot into a given pixel, and what position in space AND TIME those rays have.

This becomes very significant as we discuss motion blur.

For anyone who have read the Samples Tips page over at lamrug.org knows that mental ray normally shoots rays roughly in a grid (but with jittering, so it is not exactly a grid) which it subdivides adaptively as needed, and for motion blur, mental ray actually (in the default raytracing case) shoots multiple rays into the same spatial position, but with different temporal positions (effectively rendering the subpixel sample at more than one position in time).

An image from LAmrUG.org

Now, Unified sampling unifies (hence the name) spatial and temporal sampling. Each ray has it's own space AND time sample. And not only that, the convergence of both is adaptive, so you simply set a lower limit on the amount of rays (say, 1) and an upper limit (say, 100) and simply turn a quality knob. This tries to adaptively resolve any noise from any source, be it soft shadows, glossy reflections, or motion blur with the SAME oversampling scheme.

Sounds nice, eh? So it's a pity it wasn't included in the 3ds Max UI, isn't it?

Luckily, the FEATURE is still there, and can be reached via Scripting.

In the Beta team, a set of people generated scripts to solve this issue (there are even several), and here are a few places you can download such scripts:

Arthur Leão and Duncan Howdin cowrote this script (pictured above) which you can download from Arthur's site
at http://dimensao3.com/al/ (file itself here)

It allows you to set the parameters and by doing this improve render times with motion blur and quality of quasi-random effects such as soft shadows and glossy reflecitons more easily than in the past.

These scripts utilize the MaxScript exposure of mental ray "string options". A problem with the string option MaxScript feature is that it the state of string options is NOT saved with the .max file. However, Arthur has solved this isse with a callback in the script ... or somesuch magic, I suck at MaxScript myself... ;)

Thorsten Hartmann (Infinity Vision) wrote another version which he has posted at http://www.infinity-vision.de/blog/unified_sampling which also contains some information and test renders.

Enjoy Unification day!

/Z

MetaSL.org - MetaSL Tutorial and Reference Book/Website

2011-03-21T16:15:00.001+01:00

Hello everybody!

Today we release MetaSL.org which is a companion website to the work-in-progress book about MetaSL programming by Andy Kopra and Lutz Kettner.

This site/book is a walkthrough of the concepts behind MetaSL and will show you how to write shaders in the MetaSL language.

Now, let it be clear that this is intended as a living "work in progress site", so these are the initial chapters of the book, available online.

I quote from the page: "Chapters of the MetaSL book will be posted on the website in both HTML and PDF formats as they are written. The structure and contents of earlier chapters may change as required by the development of later chapters. The reference pages, based as they are on the MetaSL specification, will not change between MetaSL specification versions, though improvements may be made in the way the content is hyperlinked and cross-referenced."

What is available so far is the first four chapters explaining topics such as basic language concept and layout, and some of the most basic shading- and raytracing concepts.

The book also has an accompanying forum on the mental images website, where questions and feedback can be posted. You will get an unprecedented front-row seat to the evolution of this book. Enjoy the ride!

/Z

Issue in mia_envblur in 3ds Max

2011-03-03T14:24:00.001+01:00

An issue has been found in the "mia_envblur" shader as it is integrated into 3ds Max. (Read more about mia_envblur here)

Autodesk has added a Phenomenon wrapping the shader, and it was just discovered there is a typo in the Phenomenon declaration, that causes one of the parameters to not actually function. The blur still works - but only with a fixed level. The checkbox for inheriting the blur from the Arch&Design material is non-functional!

You can easily fix this yourself by opening a file named "architectural_max.mi" which in the path: <3dsmax>\mentalimages\shaders_standard\mentalray\include.

Opening the file you can search for a line which reads like this:

"mia_material_blur" = interface "not m.mia_material_blur",

Edit this line to read:

"mia_material_blur" = interface "m.mia_material_blur",

...i.e. removing the "not ".

Now, all parameters of your environment blur (including inheriting blur from the Arch&Design material) should work!

Also, some people report issues with flickering in the reflections. This can be caused by two things:

Too low resolution in the Envblur shader. The "resolution" value need to be high enough to resolve details in the original environment map.
Intermittent interaction with the "blur" feature in 3ds max "Bitmap" shader. Turn down the blur in the Bitmap shader (in the "Coordinates" rollout) to lowest possible, which should resolve the problem.

I thought this was funny....

2011-02-26T12:15:00.000+01:00

I normally don't use mentalraytips.com to post "funny" things, but I had to make an exception for this, because, well... you'll see.

When I received this little video, it literally made my day. It's the "Behind The Scenes" video for Freddie Wong's "Epic VFX Time". Freddie does little funny visual effects experiments and tutorials on his youtube channel - well worth a watch.

However, when this came across my screen, well, I couldn't help but laugh:

I've been mentioned in VFX behind-the-scenes documentaries before - but never like this.

Thanks guys. :)

However, I'd like to massively correct that I am not "the guy who programs mental ray", I am *a* guy who programs mental ray *shaders*. That's different. We are a whole team behind the software, not just me...

But still - thanks!

/Z

The Great Directory Migration - putting stuff in 3ds max 2011 (and newer)

2011-02-04T15:25:00.006+01:00

I apologize that this blog post is way overdue.

What's this about?

All over the net (including this blog) you can find instructions in how to add various shaders to 3ds Max, by putting files in certain directories in the 3ds max directory structure, namely a "mentalray" directory (with various subdirectories) under your main 3ds max directory.

Nowdays, there are two things to watch out for:

GOTCHA #1: 64/32 Bitness

First is 32 vs 64 bit. In windows, programs on a 32 bit machine live under a directory that (on an english speaking computer) is called "C:\Program Files\"

This is also true for 64 bit programs on a 64 bit computer.

However, for 32 bit programs on a 64 bit computer the directory is called "C:\Program Files (x86)\" which may throw you off.

GOTCHA #2: 3ds Max 2011 (and newer)

When Autodesk introduced the MetaSL framework in 3ds Max 2011 (which means that shaders are not necessarily mental ray shaders per se) having a subdirectory to your max directory called "mentalray" doesn't really make sense any more. But since these both are mental images technologies, having a directory called "mentalimages" does make sense.

The change was made such that instead of a single "mentalray" directory under which the three categories of shaders (standard, autoload and 3rdparty), there is now instead a "mentalimages" directory. The three categories exist under this directory, similar to before.

However, under those three directories, the distinction between "mentalray" and "MetaSL" shaders has been added.

Under those you find various other subdirectories - which under the "mentalray" subdirectory hence includes the good old friends the "include" and "shaders" directories.

Example:

To add an .mi file like for example the skinplus.mi (a mental ray "include" file) shader to be automatically loaded on startup, you want it in the "include" directory under the "autoload" category.

In 3ds Max 2010 (or older) this would have been:

C:\Program Files\Autodesk\3ds Max 2010\mentalray\shaders_autoload\include

In 3ds Max 2011 (and newer) this would instead be

C:\Program Files\Autodesk\3ds Max 2011\mentalimages\shaders_autoload\mentalray\include

Basically, the translation would be that

C:\Program Files\Autodesk\3ds Max 2010\mentalray\shaders_<category>\<dirname>

becomes

C:\Program Files\Autodesk\3ds Max 2011\mentalimages\shaders_<category>\mentalray\<dirname>

I hope this helps installing various shaders and other goodies in 3ds Max 2011 and beyond.

The Re-run-run-run, the Re-run-run (FXPhd class on again!)

2011-01-17T13:11:00.001+01:00

For those of you who missed my FXPHD course the other two times it was run... HERE SHE IS AGAIN!

More info in the posts below. Again - this is a re-run, so it is the exact same classes as before... but I will be available in the FXPHD forum for students to ask crazy questions.

See you on FXPHD!

/Z

mental ray for C4D users!

2010-11-23T12:20:00.000+01:00

Aloha folks, long time no post.

Sorry, Zap's been busy with .... stuff.

Also, some other guys than me have been busy and created this neat plugin for using mental ray AND iRay from within Cinema 4D:

It fully supports not only all the standard C4D materials, but also custom shaders in MetaSL, so this is some kick-butt powerful stuff!

Check out the website for more information, coz I must admit I am not an expert on C4D at all, and was not directly involved in this project, so I can't really answer much questions about it, sorry :)

But hey, C4D users - enjoy!

/Z

More about MetaSL in 3ds Max 2011

2010-08-23T16:33:00.002+02:00

Aloha again!

Sorry for not making a proper "post SIGGRAPH post", but I've been "post SIGGRAPH busy". And as always, me being Busy, means good things for you all.... in the future. :)

I've gotten a ton of questions about MetaSL in 3ds Max, and since the public beta mentioned in a previous post has now been discontinued (you can still use the 30 day trial if you like it will time out approximately the same time that the public beta would have timed out anyway), the interest in "what was the app actually doing and can I do it myself" has increased.

So let me explain the process 3ds Max uses to load/use a MetaSL shader:

Max uses configuration files located in the <3dsmax>\mentalimages\shaders_standard\MetaSL\Config directory to define how it works.

First there is a file in this directory named MaxMetaSLNodeTexmap.tbx. This file contains entries of which MetaSL shaders are shown in the MetaSL section in the Slate material editor.

By default, only a handful of shaders are actually in this file, but anyone can open up this file and add new entries for any of the standard MetaSL shaders that ship with max (and all the shaders in mental mill are included in this set).

So by adding a line like, for example

<palette_item type="node_class" node_class="generator_blend_ramp" image="conversion.bmp"/>

...will make the standard shader generator_blend_ramp visible in your Slate "MetaSL" toolbox! (NOTE: You must add it before the closing "<palette/>" line)

That's fine for "standard" shaders, but what about adding your OWN shader?

Well, when max is looking for a MetaSL shader name (technically, a MetaSL class name), it rummages through the file NodeToMsl_MappingTable.xml in that same directory.

This file contains entries similar to these:

<Item ClassName="Color_contrast" XMSLName="color_balance.xmsl"/> <Item ClassName="Color_gamma" XMSLName="color_balance.xmsl"/> <Item ClassName="Color_saturation" XMSLName="color_balance.xmsl"/>

This links a class name ("Color_contrast" for example) to a file that needs to be loaded to define that class name ("color_balance.xmsl" in that case).

If we further look into the file "color_balance.xmsl" (which lives in the <3dsmax>\mentalimages\shaders_standard\MetaSL\XMSL directory), we will find it consists only of this line:

<root> <metasl_code file_name="color_balance.msl"/> </root>

What we see is that this file simply loads the "color_balance.msl" file (which lives in the <3dsmax>\mentalimages\shaders_standard\MetaSL\MSL directory). Now this XMSL file could have defined a whole phenomena of it's own (of the desired class name), but in this case it didn't... it simply deffered to say "nah, to find that class, just load this MSL file, it will defined that class".

And if we were to open up "generator_blend_ramp.msl" we will find some shader code that indeed defines this shader.

So, to add our OWN shader, all we need to do are the following steps. Assume we have a simple shader that multiplies two colors, like this:

shader mul2colors {
  input:
    Color A;
    Color B;
  output:
    Color result;

  void main() {
    result = A * B;
  }
};

#1: We our shader code in a file in the <3dsmax>\mentalimages\shaders_standard\MetaSL\MSL directory in a file named multi_two_colors.MSL

#2: Create an XMSL file in the <3dsmax>\mentalimages\shaders_standard\MetaSL\MSL\mult_two_colors.xmsl that simply reffers to the MSL file, using the simple format above, e.g.
<root> <metasl_code file_name="mult_two_colors.msl"/> </root>

#3: Add an entry in the <3dsmax>\mentalimages\shaders_standard\MetaSL\Config\NodeToMSL_MappingTable.xml file for the new class, mapping the shader name ("mul2colors") to the .xmsl file name ("mult_two_colors.xmsl")
<Item ClassName="mul2color" XMSLName="mult_two_colors.xmsl"/>

#4: Finally, make it visible by adding it to the 3ds Max MetaSL Slate toolbox by adding a line to the <3dsmax>\mentalimages\shaders_standard\MetaSL\Config\MaxMetaSLNodeTexmap.tbx file (prior to the closing "<palette/>" line:
<palette_item type="node_class" node_class="mul2colors" image="conversion.bmp"/>

Note: The name of the bitmap isn't important since 3ds Max creates it's own bitmaps by actually running the shader w. it's default parameters to generate the toolbox icon.

Hope this makes sense?

ALSO, DO NOT FORGET that my FXPHD class is still running... we're in the week 5 "break week" currently. There is still time to sign up (FXPHD allows signups up until the 8:th class week). So be there, or be hexagonal! ;)

/Z

Heading off to SIGGRAPH 2010

2010-07-23T10:10:00.002+02:00

A quick note: Heading off to SIGGRAPH right... now.

Those who want to follow me do it most easily on twitter, and I may post some neat stuff on QiK once in a while:

twitter.com/MasterZap

facebook.com/MasterZap

qik.com/MasterZap

Enjoy

/Z

MRY201 mental ray FXPHD course to be RE-RUN for July 2010 term

2010-07-02T14:26:00.001+02:00

For those of you who missed my FXPHD course back in January, fear not, because it is being run AGAIN this upcoming July term!

Scroll down to my previous postings about the course for more info! Now, this is a re-run, so it is the same classes as before (with some minor updates and corrections, especially to Class #1), but I will still be available in the FXPHD forum for the new students to ask their questions!

For more info about the course click here or just go to www.fxphd.com

For now, though, I'm off on some vacation, coming back in time for SIGGRAPH 2010 in Los Angeles! More about that in a later post!

/Z

MetaSL in 3ds Max 2011 - demo

2010-06-22T12:57:00.000+02:00

After posting my last post, I've gotten a lot of questions around the MetaSL implementation in 3ds Max 2011 and the Mental Mill SE 1.1 beta. Well... to demonstrate this, I've made a little video presentation (actually a shortened version of what I showed at the EUE event mentioned two posts back).

So click here to check out the video, it's 15 minutes of me rambling....

The presentation shows my MetaSL "eye" shader (to be posted soon) run in mental mill, mental ray, 3ds Max viewport, and the Quicksilver renderer.

Enjoy! :)

/Z

mental mill 1.1 Standard Edition public beta 2

2010-05-27T10:22:00.015+02:00

Notice: There is a new public beta of mental mill 1.1 Standard Edition

One particular neat feature with this beta is an exporter I built for it that exports MetaSL shaders to 3ds Max 2011 directly from inside the mill.

The workflow is basically this:

Build your shader tree in mental mill
Select the root node
Go to File->Export
Choose the "Autodesk 3ds Max 2011 (Slate Extension)" exporter
(First time only: Select your 3ds max installation directory)
Hit "Export" button.
Start Max

Now you will see the shader in the Slate material editor "MetaSL" category.
These shaders now...

...work in the 3ds Max viewport
...render in mental ray
...render in Quicksilver
...and any other MetaSL compatible renderer!

And the coolest part is that it works even with your own custom made MetaSL shaders, in all above renderers! This is different than the MetaSL support in Max 2010 that was locked to the shader set shipping with it. Not so in Max 2011, you can build your own shaders. They compile automatically in the back and "just work". Even raytracing calls in the shaders get converted to the automatically generate cube reflection maps for Quicksliver, which is quite neat :)

Expect lots and lots of posts on this topic coming soon - for those that are curious about this workflow and want to see it up close, and see me debug some shaders live, pop up in Utrecht, Netherlands, next week (June 3-4, 2010) at www.EndUserEvent.com (see previous post)

Known Issues:

There are some known issues with the Lookup_Texture_2d node not showing in the viewport with gamma correction enabled, but I hear this should be fixed in a 3ds Max service pack (hopefully). It still works in mental ray / Quicksilver.
If Texture2d inputs exist inside a phenomena in your mill graph but are not exposed to the interface of the Phoneomenon, they will not get properly filled in when loaded into 3ds Max. To fix this, simply expose the "Texture2d" to the interface of the Phenomenon.

Find the download for mental mill 1.1 Standard Edition here

Have fun!

/Z

End User Event, Jun 3-4 2010, Utrecht / Netherlands

2010-04-25T20:41:00.000+02:00

A heads up:

On June 3/4, my good friend Joep van der Steen, author of "rendering with mental ray & 3ds Max" will be - again - hold the "End User Event".

Imagine it as a very tiny and very European and very personal mini-version of Siggraph. There are two days filled with lectures and talks and mingling, and, yeah... it's held in a bar. :) (Well, a bar with conference rooms on the sides)

Sign up now if you want to join in on the fun. I'll be speaking there about MetaSL in 3ds Max 2011 and some other mental-ray-y things.... see you there.

www.EndUserEvent.com

/Z

FXPHD, closed, done, complete, over. PHEW

2010-04-09T10:34:00.002+02:00

Well, that was an interesting ride of 10 weeks of doing FXPHD. And while I really enjoyed doing it, well, it was quite a lot of work (since I'm such a nerdy perfectionist and want to embellish everything to the border of insanity) so I won't be doing it again any time soon....

I have not heard if the FXPHD guys plan to re-run the course, at least it is not being re-run immediately for the current April term starting up in the next few weeks. And of course, if/when it is re-run, it's the same classes run again, so all I have to do then is to hang around in the forums for questions, which is much easier....

It was quite fun to see the progress of the students and I saw quite a few nice renders done by them. I think I made several people see the light of linear rendering... :)

I'll let you guys know when more similar stuff happens. Next up is EUE (more in a future post)

Also, expect some trickle-down effect for the blog. I created some nifty Phenomena for the FXPhd course that I will post here after some polish.... stay tuned!

/Z

mental ray in Round 6

2010-03-06T09:00:00.003+01:00

Check out this awesome short film by Snowball Studios called "Round 6". You may think it is a game cinematic, but it's actually a short film intentionally made in the style of a game cinematic:

Round 6 from Snowball Studios on Vimeo.

This is, of course, mental ray in all it's glory, and what I found most interesting about this is that they have a very cool production blog over at http://round6construction.blogspot.com/ where you can read many more details of the project.

Great work guys!

/Z

FXPHD update/FAQ - it's still on!

2010-02-04T10:00:00.000+01:00

Hello!

Some updates bout my FXPHD class:

I just released Class #4 of my FXPHD course 'production rendering techniques with mental ray'. We are currently having fun doing SteamPunk Robots in a real SteamPunk location:

Perhaps you want to Join the Fun?

The questions I get most often about the FXPHD classes are:

Is it too late to join now?

No. The term may be called "January10", but it is not until 8:th week of the class (sometime in early March) is it actually "too late".

Classes are released once a week over 11 weeks (there's a break week in there), and you can download them at your leisure... however, the advantage of taking the class "live" is the interaction in the forum between the teacher (me) and the students (you, and many others).

Will this class be "Max Only"

NO. As a matter of fact, beggining Class 4 I've taken steps to include explicit information for both Maya and Softimage users, as well as amended one of the earlier classes with specific Maya and Softimage info.

I still do run the major demos in Max, though.

Will there be a lot of button pushing in Max that I will not have use of in Softimage or Maya

Not really. There will be some, but I spend a lot of the time in the class teaching theory and the why of things. How you see the world, why you need to do X, Y and Z. The actual mechanics of doing X, Y and Z is also shown - but frankly, that's in the manual! UNDERSTANDING WHY you do X, Y and Z, and UNDERSTANDING when not to do Y but Q, is where the real information lies. THAT is what I teach.

I had students that doesn't even use mental ray take the class (poor lost souls... just kidding) and enjoy it!

What does it cost me? This isn't free, right?

FXPHD has nice introductory information on their site, but here's the short Zaptronic description of how it works:

FXPHD supplies 41 courses this term (called "January10", even though it stretches over three+ months). One of these courses is my course, "production rendering techniques with mental ray".

To join a term, you pay $330. For this money you get to pick 3 courses freely out of the 41 available, plus are given on mandatory "Background Fundamentals" course, so four courses in all.

Each course has, as said, 10 classes, each class being a 30-60 minute video that you can download when you want (i.e. the class itself is not "live" per se). What is "live" is the FXPHD forum behind the class where studends (you) and the teacher (me) interact and discuss the classes.

Also, on top of your 4 * 10 classes you have chosen, you get access to the first two classes in ALL courses (so you can make up your mind before you choose the 3 you want to take). So that's 37 * 2 EXTRA classes that you get thrown in.

I once computed that this alone is actually 3 solid 24 hour days of video content! Not too shabby :)

Hope this straightens out some ?'s that people may have!

/Z

Softimage defaults issue

2010-02-04T09:37:00.003+01:00

Hello!

While teaching my FXPHD course, I stumbled upon a problem I have not seen before. The error is in Softimage 2010 and (I guess) all earlier version that has the mia_material (known as "Architectural" in Softimage) integrated.

The bug is in the default values for the Ambient Occlusion settings.

You will find that the defaults for two values are flopped: AO Shadow Color is black, and "AO Ambient" is set to a 20% gray (0.2 0.2 0.2). The proper defaults are the reverse!! Also, the AO detail enhancement is off (0).

If you use the defaults as-shipped in Softimage 2010, you get an undesired 20% ambient contribution, and your AO will only apply to that light - not your indirect bounce light.

Fixing the default will give you the proper result, and not give you a sudden 20% light coming from nowhere in particular which you probably never wanted, AND will let you use the AO to enhance the detail of your indirect illumination, as the Lord* intended.

Hope this helps!

/Z

* = That would be me in this case ;)

Introducing - my FXPHD Course - 10 weeks of mental ray training

2010-01-01T22:00:00.006+01:00

Welcome to the new year, I hope the holidays were nice to you all....

...so. I have some news:

It has been in discussion for some time (I think I may have mentioned it before), but now, it has finally come to pass:

In the January term of FXPHD, I will be teaching a mental ray course named "Production oriented rendering techniques with mental ray". Yay!

FXPHD is an online training site run by Mike Seymour, John Montgomery, Jeff Heusser and friends (who also are the people behind FXGUIDE, a VFX oriented news site I suggest you also check out if you havn't already)

Note that these courses are not free, but they are not extremely expensive either - and considering the classes run for ten weeks with full participation of the professor (that's me, in this case) in the forums for questions about the class, it's really a pretty good bargain, IMHO.

The standard FXPHD deal is that you pay for a package where you get to sign up for three of their courses. But the cool thing is that you get to see the first two classes of each course anyway, so you can spend your first two weeks of the term browsing around before you make up your mind to pick a (set of) class(es). Also, a freebie "Background Fundamentals" class is always included, with all sorts of topics.

(If you sign up as a new user, and there is a refferal field, fill in "MasterZap".

Here's my teaser clip for the class:

(If you want the FULL FXPHD orientation video (from which the above is my "segment"), it can be downloaded here.)

This course will teach techniques and concepts for rendering realistic, physically based CG elements in a visual effects context (i.e. for integration into live action shots). As it is a hands-on course in using Mental Ray to do these things, it will start with a fundamental treatment of everything from light and pixels through to cameras, response curves and compositing, as well as "learning to see". The course will be performed using the 3ds Max application, but most things apply to Maya and Softimage as well.

The ten classes will be rougly divided like this (subject to change based on feedback):

Class 1:
Pixels vs. Light - What is a pixel? The units of light, and how they map to the RGB values we encounter every day. Shows how the math we apply to pixels can break, and how, if we are not careful, two plus two can end up ten.

Class 2:
Lighting - Understanding the quality and quantity of light. Understanding how real-world lights map to computer graphics lights. Understanding how light gathers and reflects off a surface.

Class 3:
Cameras - Understanding how a real world cameras function map to their computer graphics counterparts. Understanding what film and digital cameras do to the image before you even see it.

Class 4:
Materials I - Using the physically based Arch&Design material to simulate real world surfaces. Learning to see the world, so that one can translate it to CG.

Class 5:
Materials II - More about materials. Using the mental ray skin shader for realistic characters.

Class 6:
Interaction between CG and the Real World - Using the production library shaders to seamlessly integrate CG objects in real-world background plates with reflections, bounce light, shadows, etc.

Class 7:
What Not To Do - Computer Graphics is full of old "traditional" techniques that has stuck around for many years, but that are in conflict with proper physical rendering, and should be avoided. Just because the button is still there doesn't mean you should push it.

Class 8:
Compositing - How stuff that comes out of the renderer goes together, and what can (and should) and can't (and shouldn't) be delegated to compositing.

Class 9:
Technical topics such as sampling, flicker elimination, memory management. These classes may also adress issues that has come up in the forum as needed.

Class 10:
Continuation of class 09

Check it out! I am very excited to do this class, and I welcome you all to join FXPHD!

/Z

Merry Christmas Everybody

2009-12-23T20:52:00.003+01:00

Another year is coming to an end. The next year will kick off with... something fun. But for now - Merry X-mas and a Happy new year!

I will leave you all with a thing I did 10 years ago; I used to have a band called Beat Symphony together with a guy called Michael Gilboe from the US (yes, I used to be into music - crazy, innit?). The whole idea was that we were "100 years retro", and we did a form of 19:th century Baroque-techno.

This was our Christmas Song:

You can see it in higher quality in the original flash version here, (although none of the links at the end work anymore).

Hope the new year will treat y'all nicely, and that 2010 will be the Year of Greatness for everyone!

/Z

Fire and Ice - rendering Diamonds and Gems in mental ray

2009-11-13T10:18:00.011+01:00

They say Diamonds are a Girls Best Friend, but they can be a poor rendering guys worst nightmare.

One of the reasons is the characteristic property of fine diamonds known in the gem business as "fire" - the nice "pretty colors".
These stem from the fact that Diamond is a material with very high dispersion. It is also coupled with the fact that the "cut" of a diamond is specifically made to enhance the "fire" (dispersion) and "brilliance" (ability to reflect light back to the viewer) as much as possible.

But even before we get to the actual dispersion part of things, lets try to see what it takes to render realistic gem's without it first.

Setting up a scene for Gem rendering

We start with a ridicolously simple 3D model. Since I can't model worth crap, I downloaded a diamond cut according to the classic "round brilliant" from here, and made this supercomplex scene:

First, make sure you have your gamma correction enabled, diamonds, like all physical things, should be rendered linearily.

Not gamma corrected - ugly

Gamma corrected - good

Now we need some decent lighting. We need to follow physics as much as possible. Especially we want to avoid nonphysical "hacks" like specular-only lights, lights without shadows, and other things. We really want to light this in the same way a real photographer would light his scene, with realistic lights with all their realistic effects.

In 3ds Max the easiest way to do this is to use the Photometric lights. This will become especially important later when we get to the caustics, because the Photometric lights automatically gives us the proper photon energy for free. That is a little bit more work to achieve in Maya or Softimage (XSI) because you have to set the photon energy up manually.

A key point here is that we make them Target Lights (i.e. spotlights). This is so we get the most efficient distribution of photons. If we didn't give them a direction to shine, our photon emission phase would be much slower because so many photons would get lost in empty space. Make sure you aim the lights where they are needed - this is especially true with caustics.

Since we are using photometric lights, this also requires us to use an exposure control. We will be using the mr Photographic Exposure control, and we need to make sure to check the "Process Environment and Background" checkbox:

We also want to make sure they are area lights. This gives us the nice soft shadows and "soft" lighting that you would use for an artsy product render like this:

Point lights - hard shadows

Area lights - soft shadows

So we enable area lights:

Now these two arealights are not enough, we need indirect light, and to light the scene from the environment as well. To do this we need turn on Final Gathering.

In Maya and Softimage, the very act of doing this will implicitly light the scene from the environment. This doesn't happen in 3ds Max unless we put in a "Skylight". So we add one of those to the scene, and very importantly, set it's option to "Use Scene Environment".

Now we have a little more light:

We are using a default Arch&Design (mia_material) on the gems.
Let us make it more gem-like by a) turning our diffuse to 0.0,
and b) turning our transpacenty to 1.0:

Diffuse = 0.0

Transparency = 1.0

The automatic energy conservation of Arch&Design (mia_material) already makes this a decent looking transparent looking thing... transparency is complete, but still "overridden" by reflections, and the reflections do depend on angle, just like on real dielectric materials. However, by default it is not basing it on the index of refraction, but a custom curve. We need to fix that by setting it to IOR mode!

This makes our transparency a bit "clearer":

Curve mode

IOR mode

The scene is still looking rather dull with the gray background. Diamonds (like metals) are not so interesting looking in-and-of themselves, but area all about reflections and very very bright "pings" of light. Some people may be tempted to cheat this with a bunch of specular only lights, but why cheat when there is a real reason for such effect - reflections of Bright Things.

And what's the easiest way to get some Bright Things, if not an HDR environment map? Lets slap in some interesting HDR environment map. In 3ds Max you do this by adding a Bitmap to your Environment slot, and make sure to set it to a spherical environment: (Note: When doing this you may need to play with the Physical Scale to avoid having the environment map render dark, see here)

This should give us something much more interesting to look at. And note how the background lighting changed in tone to match the environment? This is because Final Gathering is picking up the new environment and getting it's lighting from there:

Actually FG is even picking up some of the concentrated bright spots and creating a form of "faux caustics". We will get to real caustics later, but for now it is looking pretty.

To make our image look nice, we are using the mr Photographic Exposure control. To make it even nicer we are going to do some modifications.

First, images like this, where we want to focus on some nice center object, always benefit from a bit of vignetting (darkening of edges):

Secondly, since these are diamond renders, and we truly want strong "pings" of light, we should turn up the highlights, to make the really bright bits be really really bright:

These are the knobs we used to do this:

And here comes a final little subtlety. This is really hardly a visible change, but I like it. The model is made with absolutely perfectly sharp edges. And a Jeweller will want to sell you on the idea that his diamond is perfectly flat with totally sharp edges.

But reality have no such thing as 100% sharp edges, so I love to throw in a teeny bit of edge rounding, which will make edges catch "glints" and look more realistic. Cue the mental ray render time round corners shader thingy, and you will get...

...this. Yeah, not such a big difference, I know. It does more on other shaped Gem's than the round Brilliant cut, though, so I still suggest you use it.

Taking a shortcut

Another way to quickly get to the place we are now with the material, and be certain that all the settings make sense, is to base it on the Physical Glass preset. All we need to do is to load the preset, and set enable the corner rounding feature (which is off in this preset), to get a very quick and decent result:

However, we are using the default index of refraction of glass, which is 1.5.

The IOR of diamond is 2.42 - so let's change that:

To really make sure we get every single nice "glint" and "ping" of the material, we will disable a speed optimization in the material intended to skip "unnecessary" reflections on the inside of glass objects, which tend to be very weak. But we don't want to loose any light, so we turn that feature off.

Color Gems

Now these gems look a tad blue. This is because the "Physical Glass" preset introduces some blue. Before we go further with the diamonds, lets discussed coloring our gems for a moment.

The quick and "obvious" way is to reach for the transparency color swatch, and set this to a color. While this gives something (which can look pretty nice), it is not physically accurate:

This is because it modifies the color of the ray "at the surface" of the object, whereas real colored transparent object modify the color of the ray gradually as it travels through the medium.

Looking at the gems above (rubies, perhaps?), the small ones are just as deeply red as the big one, and the tip of the big one is just as deeply red as the thickest part of it. That doesn't look... correct.

What we need to do is to enable attenuation through the medium instead. To do this we need to set our transparency color back to white (basically, treat the surface itself as completely transparent), and move to the falloff settings within the material:

We can use the same color as before, but we just have to set up a distance; at how thick a piece of material would you expect to see that color? Thinner than this will be less colored, thicker will be more deeply colored.

NOTE: It is important that this color has no component of 100%, and no component of 0%. If you were to set it to 1,0,0 red, it would be just as bad as the nonphysical setting. A better "red" would be something like 0.9,0.1,0.1, meaning, it lets through a lot (but not all) red, and very little (but not zero) of the other colors.

Here is our result:

But ideal diamonds are pretty much completely transparent, so for our excercise we will turn this falloff inside the mateial off completely! Uncheck the "Max Distance" and get:

We are getting somewhere. One further thing to ensure the largest amount of nice shiny "pings" in our material is to set our area lights to be "visible". Because most glints in a diamond is a reflection of an actual light. Turning this option on will render the area lights as superbright surfaces, that will then be seen refracted through our diamonds.

Caustics

Finally, it is time for those elusive Caustic effects. First we must make sure the material is set up to actually do caustics, since Arch&Design (mia_material) has an explicit option to NOT do that. If we used the "Physical Glass" preset, this will already be set up for us, but lets make sure:

Also we must make sure that caustics are turned on in the render itself. To get nicer "sharp" caustics, I tend to lower the number of photons per sample, and set the filter to "cone".

Generally, the Multiplier should always be 1.0, but we can allow ourselves some artistic licence here and turn it up a tad. But in general, since we are using the photometric lights, we should be getting the physically correct caustic brightness out-of-the-box. If they seem to weak, its probably beacuse people intuition of how bright they "should" be tend to be very overestimated.

We get this image:

Notice how the shadows actually became darker? This is because they were previously faked by simply attenuating the light a little bit, bit now the light is properly concentrated in the caustic effect instead. So this is correct.

A final touch on this image is to apply some glare.

Both real world cameras and human eyes perceive a "glow" around superbright objects, partially due to scattering in the atmostphere, but actually much more due to scattering in the light path (lenses) and the imaging surface itself (the film, the CCD, or our retina).

When adding the "Glare" output shader, we get the following image:

Notice how it looks much brighter without actually being any brighter at all. That's psycho-optics at work. A white pixel just looks white. A white pixel with a glow around it, and you'll be reaching for your sunglasses.... :)

And now - finally - time for Dispersion

Dispersion is when different wavelengths refract differently. I guess the most obvious case of this is a rainbow.

Real sunlight is a spectra containing basically an infinite number of wavelengths at once, and each of the different wavelengths will refract slightly differently... i.e. when a sunray hits a surface, one would (in principle) need to trace an infinite amount of rays around the scene to get the "real" effect.

Computers aren't very fond of doing an infinite number of things - at least not if you want them to ever finish. So there are several ways to simulate this w. various techniques.

The technique we will be using here is a very low-tech one - we simply render the scene multiple times with slightly different IOR's, colorize each of the renderings based roughly on the "color" of that wavelength, and combine the result. Et voila, we have a dispersive render.

To aid in this I slapped together a little piece of maxscript. Go to your Maxscript menu and choose "Run Script". A small dialog will pop up with some options.

Simply put, the script will render your image multiple times, while modifying the IOR of your material. But to do this, it needs to know what "your material" is.

It tries to be clever and find any material named "Diamond", but if it doesn't find it, you will have to click the "pick material" button, and choose the material from the scene that you are using (in Instance mode).

Then you need to set the IOR you want it to use, and how the amount of "dispersion". In gemology "dispersion" is pretty much defined as the change in IOR across the visible spectrum, so I tried to mimic this in the script, but it's a bit hacky and probably not accurate at all, so take it for what it is.

When you are done setting up, you can hit the "Do Dispersion Render" button. (Note: The script does not save the image, you will need to do that yourself from the image window)

The "3 bands" mode does three renders, one each for red, green and blue, and looks like this:

The "6 bands" mode does six renders, for red, yellow, green, cyan, blue and magenta, and is a more subtle effect, but more likely to yeild a "nicer" looking rainbow effect:

And as a final pièce de résistance, we can enabled depth of field on the camera.

In 3ds Max, this is done by using a 'multi pass render effect' on the camera. This is a bit of a misnomer because it isn't really a "multi pass" effect at all, but it re-uses the UI concept of other 3ds Max "multi pass" effects, so that's where you'll find it. Sorry, it wasn't me who put it there :)

You simply set the f-stop of the camera, and you will get the physically correct depth of field assuming that

your scene units are properly set up, AND
your Aperture Width (in the render dialog) makes sense.

That will give you this "ultimate" render - and we are pretty much done:

Of course, we can exaggerate the dispersion effect for arts sake (simply turn up "Dispersion" a bit):

Finally, the script also supports a somewhat hacky "chromatic abberation" mode, where it introduces the Lume "Distortion" lens shader, and modifies the pincushion/barrel distortion slightly for each of the colored renders, if you want to go really Crazee. This is one result of that:

Hope this was helpful.

Unfortunately, you can't cash these diamonds in a bank, nor sell them on eBay...

/Z

Animago Conference Masterclass

2009-10-14T22:13:00.003+02:00

On October 29:th and 30:th is the Animago Conference including the Animago Awards. This occurs in Babelsberg (which is the Berlin version of Hollywood).

On Friday October 30:th, at 9AM, I will be holding a mental ray Masterclass there. See the page above for more details, and stuff.

Welcome if you are in the neighborhood!

Update:

I will try to send out some updates to twitter, Phazeb00k and QiK as the event unfolds, feel free to follow:

/Z

MasterClass now in 9 languages

2009-10-07T16:57:00.002+02:00

The link is still the same, click here.

But if you didn't understand what I was rambling about before, you can now not understand what I ramble about, subtitled :)

Enjoy.

/Z

My appearance on the FXGuide Linear Workflow Podcast

2009-09-30T11:55:00.008+02:00

FXGuide Linear Workflow Podcast

Mike Seymour of FXGuide/FXPhd lost in China

I was recently interviewed by my good friend Mike Seymour over at FXGuide.com about linear workflow and linear compositing in a visual effects context.

You can listen to us ramble on the topic for nearly an hour by right here, or you can read a bit about it and comment here where you can also subscribe to the podcast for more glorious FX geekiness.

In the podcast, I mention Stu Machwitz about 1024 times. You can find Stu's blog over at ProLost.com (He doesn't consider it profound - get it?), and Stu even wrote a very lovely note on his blog in response, very heartwarming, thank you Stu! *wipes tear from eye*

Errata

Of course, as is when I ramble several run-on sentences for almost an hour, som errors creep in. After listening to it, I realize I misspaketh on a couple of places (disregarding some grammar snafu's, after all, I'm Swedish, darnit!)

I incorrectly attribute the creation of the EXR format to Pixar, I of course meant ILM. Apologies to both parties.
When describing the math of the "screen" composit operation, I say "sum" where it should be "product", i.e. the correct sentence should be "one minues the product of one minus each of the components". Duh. I.e. (1 - ((1 - A) * (1 - B)))

FXGuide and FXPhd

If you guys don't know about FXGuide, and their companion training site FXPhd, I suggest you check them out. These guys are very passionate people with a great knowledge of visual effects techniques, and they do some very nice stuff.

LinearWorkflow.com

Going to LinearWorkflow.com today isn't terribly interesting, but some stuff is coming up in a not too distant future. I just have other higher-priority work happening right now... stay tuned... :)

And, BTW, don't buy that stupid T-shirt, it's CafePress and it actually came out not-so-pretty.

/Z

mental ray tutorials by Jeff Patton

2009-09-14T19:59:00.001+02:00

If you follow this little link you will end up on a place where you can purchase (cheaply!) tutorials by my good friend and mental ray guru Jeff Patton.

They cover all sorts of topics from stuff all the way over to things ;)

Check them out!

/Z

Digital Tutors mental ray training

2009-08-25T12:16:00.003+02:00

My friend Sylvain Berger (who also runs a rendering blog over at http://kobayashystips.blogspot.com/) alerted me to availability of mental ray training over at Digital Tutors.

You can sign up for an account and access a subset of the trainings free of charge as samples. One of these free samples, which Sylvain points out, happens to be a really nice training on using the production shaders in Softimage, which I can recommend.

For those Softimage users who took my masterclass (below) and were annoyed by all the UI happening inside 3ds Max, and wanted to find those equivalent buttons and shaders in Softimage, this training is for you.

/Z

The SIGGRAPH 09 masterclass is LIVE

2009-08-03T17:20:00.009+02:00

Clickety here for the masterclass "GIANT ROBOTS: Using mental ray shaders for introducing CG elements into real shots".

You need to register 1st, but it's free!

Enjoy me rambling for 1.5 hours ;)

UPDATE: Link is now back online - but it seems to require Flash 10. I had Flash 9 in Firefox, and it did not work, but never gave any error message.

/Z

SIGGRAPH Masterclass: GIANT ROBOTS (Using mental ray shaders to integrate CG elements into real scenes)

2009-07-31T19:10:00.003+02:00

Hello Everybody!

Sorry for being incommunicado for a while. I've been busy, and I've been on Vacation.

On Monday, SIGGRAPH kicks off, and for the first time in many years I will actually not be going there... however, I will be there "in spirit". As usual, I have an Autodesk MasterClass running, only, this year the MasterClasses will be ONLINE, and not live in-person things.

My class is called "Giant Robots: Using mental ray shaders to integrate CG objects into real scenes", and it will be available from August 3rd 2009 somewhere on www.the-area.com

Here's a teaser:

I'll let y'all know when the actual class is on, and give a direct link to it.

Enjoy... and for those actually going to SIGGRAPH in New Orleans... have a beaker for me ;)

/Z

MetaSL shader library opens

2009-06-04T15:04:00.004+02:00

Just went live....

This is the first glimpse into the MetaSL material shader library....

http://materials.mentalimages.com

I will post more details later, but until then - have fun ;)

/Z

"Star Wars: Old Republic" Cinematic

2009-06-02T11:37:00.003+02:00

Blur Studio... again*. And using mental ray.... of course....

Video Games | Star Wars: The Old Republic | E3 09: Jedi vs Sith Cinematic

XBox 360 | Playstation 3 | Nintendo Wii

* = You can tell from all the blowing embers ;)

/Z

The joy of Airports

2009-05-27T11:15:00.003+02:00

Just a short reminder of the EndUserEvent.com event. Posted from the airport. :)

C U There.

As in all my "appearances", check for QiK updates and tweets for last minute... stuff.

/Z

3ds Max 2010, MetaSL and mental mill

2009-05-15T12:26:00.007+02:00

Wouldn't it be fun if....

While working in the viewport wouldn't it be nice if the thing you rendered was faithfully represented in the viewport? At least as faithfully as technically possible?

Wouldn't it be neat if the left part of the below was the final render and the right part would be what you saw in the viewport, while working with it?

(click to enlarge)

Oh wait - that is exactly how it looks in 3ds Max 2010! Oh no, how can this be? Is it magic? Is it elves? No, it's MetaSL, and mental images mental mill technology.

What happens in 3ds Max 2010 is that several of the shaders has been given an implementation in the MetaSL shading language. MetaSL is mental images renderer agnostic shading language. When this shading language is taken through the mental mill compiler, out the other end drops something that can fit multiple different graphics hardware, as well as several different renderers!

This way, no matter if the graphics hardware is NVidia or ATI, you will see the same thing (or as close as the card can afford to render) using only a single MetaSL source shader.

Viewport accuracy

Look at this image, which is the difference between the render (on the left) and the viewport in the previous version, 3ds Max 2009:

(click to enlarge)

Notice how horrible the viewport (on the right) looks, how harshly lit, unrealistic, and oversaturated it looks? The thing to take home from this is that the main reason that this looks massively different is that the image on the right is neither gamma corrected, nor tone mapped.

I mention this to illustrate the importance, nay, imperativeness of using a proper linear workflow, with a gamma corrected and tone-mapped image pipeline.

So while the lighting and shading itself is much more accurate in 2010 than 2009, the key feature that really causes the similarity between the render and the viewport is the tone mapping and gamma correction.

But naturally, the additional accuracy of the shading and lighting drives this home even more: See below a couple of different lighting scenarios, and see how well they match the render (again, render on the left, viewport on the right):

(click to enlarge)

After playing around a bit (tip; use the 3ds Max "light lister", you can get:

(click to enlarge)

So, using this feature, with the help of the MetaSL technology, you can make a decent set of lighting decisions and "look development" in realtime in the viewport. That's pretty neat, if I may say so myself ;)

So what about mental mill

Now nothing of the above is the end-user using mental mill. It is still using the mental mill compiler "under the hood"; MetaSL versions of 3ds Max shaders are compiled for the hardware, and used in the viewport.

But in 3ds Max 2010, the end user can also use MetaSL and mental mill directly. And yes, not only for hardware rendering in the viewport, but for mental ray rendering as well!!

First, please note that this is a 1st step integration of mental mill into 3ds Max. It has some issues (we know some quite well), and even a couple of bugs snuck into the final release (we are also very aware of these). But the general workflow is that you:

Create a shade tree inside the mental mill Artist Edition that ships with 3ds Max
Save this as an .xmsl file
Insert a "DirectX material" (yes, this makes you think this is only for HW rendering, since in the past "DirectX material" was only used for such things)
Load the .xmsl file into it
See the material in the viewport and render it with mental ray!

Now, as I mentioned above, there are some known issues in this 1st integration, to be aware of:

In mental mill you always have to build a Phenomena, not just a free standing shade tree. So your workspace in the mill should contain a single Phenomena representing your new material.
The last node must have a single output. This is actually a bug, and it will be fied, but for now, if your root node has many outputs (like for example the Illumination_Phong does), just pipe it's main output through some other shader (like Color_Brighness or similar) to make sure the final output node only has a single output.
Due to a difference in texture coordinate handling in 3ds Max mental ray and MetaSL, UV coordinates must be connected explicitly. So if you include, say, a texture looup node, you must include a "State_uv_coordinate" node to feed it coordinates. Inside mental mill you will really not see any difference, since the built in "default UV's" work there, but without doing this mental ray will render it incorrectly.
There was recently discovered an issue with localization; it seems that if your Windows system is set to use "," rather than "." for the decimal separator, this causes an error in interpreting some MetaSL code. For now, the workaround is to change your windows decimal separator settings to "."; sorry for the inconvenience :(
While you can change the shader in the mill and re-load it into the DirectX material and see the viewport update, the mental ray loaded version of the shader will not update automatically; be careful about this. You can force an update by renaming the phenomena and the file so mental ray loads it as a "new" shader.

Having taken the above things into account, though, your MetaSL shader should render pretty much exactly the same in mental ray as they appear in the viewport!

Some really snazzy things can be rendered thusly.

mental mill Standard Edition

The "Artist Edition" of mental mill sipping with 3ds Max can only work with the shipping nodes, not custom MetaSL nodes. It can also only export hardware shaders. (While this may sound like a contraditction to what I said above, note that you are not exporting the shader from mental mill in the 3ds Max 2010 workflow, you are saving the mental mill project (.xmsl) itself, and it is 3ds Max that is able to load this and render it in mental ray.)

If, however, you are a shader developer that want to write custom MetaSL shaders and render these in both mental ray and see them in the viewport, you need the mental mill "Standard Edition". This product can be purchased over the newly snazzily updated www.mentalimages.com website.

Enjoy the fun!

/Z

my mental ray talk at the End User Event

2009-04-27T21:25:00.008+02:00

Hello Everyone!

Those of you who enjoy watching me ramble endlessly (yes, such people exist), and don't think traveling to Utrecht (A short 30 minute train ride outside of Amsterdam), have nothing better to do on the 28:th and 29:th of May, and think the idea of a whole bunch of cool 3D people meeting in an actual bar is a good idea, should probably check out the End User Event

We'll all meet here, at the Florin

This event is arranged by my good friend Joep van der Steen, author of the book "Rendering with mental ray & 3ds Max. The event is a kind of meet-and-greet get-together combined with a bunch of masterclasses and talks; sort of like a microscopic version of SIGGRAPH, but in a small Dutch bar in a very nice (not so) little town.

Feel free to sign up at www.EndUserEvent.com, I think you will find it an enjoyable experience, and there is many things to learn...

Speakers include yours truly (about mental ray), my collegue Ruediger Raab (about mental mill and MetaSL), as well as many other great people like Ted Boardman (depicted on the right), Niel Blevins, Allan McKay, as well as Ken Pimentel, product manager for 3ds Max, and many many others.

I'm doing two sessions there:

* Gamma and Linear Workflow
* mental ray production rendering tricks & tips

Meet you there! Sign up now while seats remain!

/Z

Fantastic Plants

2009-04-21T15:06:00.002+02:00

Click the image above to see one of the most amazing foliage/grass/etc rendering I ever saw, any renderer, any time. To know it was done with sun&sky, mia_material, and mental ray, warms my heart.

Five stars. Times ten.

/Z

FumeFX for mental ray Released

2009-04-02T13:36:00.002+02:00

...some time ago, it seems. And I forgot to post about it - sorry.

For those who saw me demonstrating FumeFX rendering in mental ray in singapore, or heard me blabbing about it elsewhere, well, maybe I should have mentioned that it is now actually released? Well it is. Head over to Sitni Sati for a look:

www.AfterWorks.com

Enjoy.

/Z

Benjamin Buttons Beautiful Bytes

2009-02-25T14:04:00.008+01:00

Sorry for not posting for so long, I've been busy. Me being busy is often a good thing for all of you reading, although it tends to take a while from me being busy until you notice. Since what I'm doing isn't out there yet, lets ramble about something else instead:

Recently, a movie went up in theaters called "The Curious Case of Benjamin Button" starring some guy named Brad Pitt ... Hmm, that sounds familiar somehow... :)

Anyway, I have a special relationship with the effects in this film, because all the pretty stuff you see is done in mental ray, which makes me happy. (Yeah, I'm easy to please that way, LOL).

There is an almost ridiculously pretty website dedicated to The Visual Effects of Benjamin Button that I suggest you visit, if not only for the beautiful design of the site itself.

Digital Age

A lot of the "old benjamin" work was done by Digital Domain, and I suggest you check out their very cool breakdown of the process. Brad Pitt's digital head replacement was rendered in mental ray and is, I must say, probably one of the best skin shadings put to film to date.

Digital Youth

Hydraulx, and their sister company Lola did a lot of the "youthenizing" effects both on Pitt and Blanchett. I actually had the pleasure to see first hand the de-aging work on Pitt when I visited Hydraulx (which can be witnessed earlier in this very blog), and I had no idea at the time of the significance of the de-aged Brad Pitt I was being shown.

What was truly interesting about the Lola de-aging process is how manual it is. Its as far from "push a button and the computer does the work" that it can possibly be. Quite the opposite, it's nearly a matter of pulling every pixel manually from one place to another, the computer just helps with doing it over multiple frames, but even that requires TLC to look nice. I applaud the work here.

And Hydraulx/Lola also did digital head replacements of Kate Blanchett onto a professional ballerinas body, again using mental ray, and good 'ole misss_fast_skin shaders.

The Digital Skinny

Its fun for me, as the father of the good o'le mental ray skin shader, to see my little baby all grown up.

When I was in Singapore (see earlier in this blog) I met with Paul Hellard and friends from Ballistic Publishing and flipped through almost every one of their various computer art books (which I suggest y'all go and buy because they are exquisitly printed), I couldn't help but notice (to my poorly hidden personal glee) the amount of character renderings that were done in mental ray and with my o'le honey misss_fast_skin shader.

If you havn't checked out the mental ray skin shader, I suggest you try it, there are some posts in this very blog about it (searching for "skin" is a good start).

I close off this post with a video from TED.COM (if you are not a TED nut, I invite you to be one from today) about giving Benjamin Button his face.

I hope to be posting more again Real Soon. Meanwhile, follow me on twitter for shorter bursts of randomness that doesn't go into this blog.

Thank you for your time!

/Z

Merry Christmas Post

2008-12-22T09:30:00.004+01:00

My render from Jeremy Birn's lighting challenge

'ello 'everybody, and merry christmas, and all that Jazz!

Yes, I'm back from SIGGRAPH ASIA in Singapore. I couldn't get so much net connection so there wasn't much of the promised "reporting"; I apologize profusely. For the totally curious, there are some random pictures here and some cellphone video here.

SIGGRAPH ASIA was overall a very nice experience. It was small (Pixars Tony Apocada compared it to "US Siggraph 10 years ago") which was a good thing - the US SIGGRAPH's tend to overwhelm. Only drawback of Singapore; drinks way too expensive ;)

And there was an Electronic Theatre (see last post)!

The Masterclass went very well, many special thanks to Mike Seymour from FXGuide who not only was my MC for the Masterclass, but also kept up with my 175 page powerpoint, and knew which page I had to return to when Powerpoint decided to crash yet-another-time. Note to Self: Keynote, pre-prepared DVD, or anything... ANYTHING but Powerpoints next time!

Speaking of next time, unless the economy implodes further, I'm tentatively signed up for doing a class next year in New Orleans. Nothing signed up for next SIGGRAPH ASIA in Yokohama, Japan, though.

For me, I will be trying to spend the remaining shivering pieces of the year w. my family, enjoy the festivities, eat the stuff we Swedes eat, and celebrate the most holy thing on Swedish Christmas: Donald Duck.

I part with a little Christmas Gift from (again) my friends at Blur Studios (who I must add was a great help in providing me with eyecandy for my Siggie presentations); you may recall I posted a while back about an event where they talked about their Warhammer cinematic. Well, this event was filmed and is now available online, clikety here and enjoy over 2 hours of rendering, animation, crowd/hair/cloth sim, modelling and rigging geekiness!

With that, I bid adieu for 2008.

Marry X-mas and a happy new year!

/Z

Electronic Theatre FTW!

2008-12-13T05:26:00.006+01:00

I sit here outside the Eletronic Theatre at Siggraph Asia 2008 posting this, waiting to get in. The Electronic Theatre has always been a cherished Siggraph event, the highlight of the entire conference.

Yet, this year, in Los Angeles, there wasn't one. In the opinion of me, and many others, this was a disasterous move.

My good friend Mike Seymour from FXGuide (who was also nice enough to MC my Masterclass) has started an online petition to bring it back, so when we go to New Orleans in 2009, this Gem of the computer graphics industry will be back in it's proper forum, to spread the digital joy we all so desperately crave (oh, how poetic!).

So please, if you are a Siggraph nut, head over to and sign it.

Thanks. I'll now go in and enjoy the show...

/Z

Singapore Setup Session

2008-12-10T03:20:00.008+01:00

I arrived alive and well in Singapore, almost immediately ran into Duncan Brinsmead from Autodesk (pictured here on the left) and since we had some free time we walked around Singapore, and even took a trip on the "Singapore Flyer", which is the Singaporean version of the London Eye thingy.

As it happens, both Duncan and myself are doing presentations at tonights Autodesk User Group event.

So for us, today is "Teh Big Setup Day" for this presentations, as well as the booth theatere stuff.

For most of the week, I'll be alternating between the Autodesk and NVidia booths. I also hear Autodesk is streaming their booth theatre presentations over the net this year (see link below).

On Friday december 12:th, the 3 hour version of my "Miracles and Magic" mental ray masterclass will be held. It's in the convention center, but note it's an Autodesk masterclass and hence requires a ticket beyond the siggraph one.

More information on User Group event, Masterclasses, and Streaming..

/Z

Up up and away....

2008-12-07T14:24:00.003+01:00

I'm at the airport awating my first airlift enroute to SIGGRAPH ASIA in Singapore.

As a precaution, I took the photo on the right of my bag, so if it gets lost, I can show people what it looks like ;)

Smaller updates of my travels and wherabouts will be on Twitter, so follow me there, please.

If I am in Wifi range, I may show up on the FRING thingamabob on the right side.

Also, there may be QiK updates now and then.... stay tuned, same zap time, same zap channel....

/Z

Event: December 4:th: An Evening with Blur Studios

2008-12-03T15:13:00.004+01:00

On thursday, december 4:th, 2008, Blur Studios will hold a presentation about their "Warhammer Online" cinematic, and how they used mental ray for all of it.

The event is in Hollywood, CA, and is free of charge.

Details are here.

UPDATE: The event is now online here

/Z

Singapore Sling: SIGGRAPH ASIA 2008

2008-11-21T08:56:00.004+01:00

In December, I am flying to Singapore to attend SIGGRAPH ASIA.

Singapore. I think.

This will really be my first visit to this corner of the world, so it will be interesting. Assuming the current planning remains, you can most likely find me around our mental images corner of the NVidia booth, as well as doing mental ray demos in the Autodesk booth. I'll be tweeting as well, as usual.

Among other things, one thing I will be doing at SIG' ASIA is to do a re-run of my masterclass from SIGGRAPH 2008 in Los Angeles, entitled "Miracles and Magic".

It was clear I had tried to cram way too much stuff to fit in the 1.5 hours I had; I had to skip every single live demo, and leapfrog little gems to just to get through it all. But I did get through it all, at a breakneck pace.

The Audience looked somewhat like this:

So... the idea here is to re-do pretty much the same masterclass, but as a 3 hour version. This would give us a more ... relaxed... pace, and the demo bits would actually fit!

So, to be totally clear. If you were at my Autodesk masterclass (not the "SIGGRAPH Course" on "HDRI for Artists") held at the Westin Bonaventure in Los Angeles, you already saw this, but very ... quickly. :)

So if you weren't in L.A, and are interested in the same topics, feel free to attend. The blurb for the class reads as follows:

The course will focus on photo-realistic rendering in mental ray in the context of visual effects, as well as for product and architectural visualization. The session will open with a quick introduction to photometric concepts followed by a practical guide to a linear workflow and why proper gamma correction is imperative. It will then move on to efficient techniques for achieving highly realistic results when combining CG and live action by combining existing tools together (e.g. the architectural and production shader libraries), techniques for rendering flicker-free animations with Final Gathering, and tips for conserving memory.

For more information about attending the Autodesk Master Classes, go here.

/Z

The Joy of a little "Ambience"...

2008-11-05T12:04:00.010+01:00

As usual, when the same question pops up in multiple places, I tend to turn this into a blog post. The question I was asked recently was how to use ambient light in mental ray (specifically, in mental ray in 3ds Max), because people were confused about the lack of an "ambient" slot in, say, the mia_material (Arch & Design) shader.

I will try to explain this here.

THEORY: "Ambient Light" and "Occlusion" - a primer

Back in the day...

Traditional computer graphics, with no indirect lighting of any kind, would by default look like this; here's a scene lit with a single shadow-casting directional light:

I.e. shadows are pitch-black, with no realism whatsoever. You can't even tell that the yellowish rectangular thing at the bottom is a table that has legs!

So a couple of tricks were introduced. One ugly, unrealistic hack was "shadow density", i.e. the ability to say "when light from this light is in shadow, only x% of it actually disappear". So you could set things like "Shadow Color" and "Shadow Density", which you all understand is completely absurd and totally contrary to any form of sanity and logic.

An opaque object either blocks light, or it doesn't - it doesn't just randomly go "Oh I block 47% of the light". That can't happen (outside of actually transparent objects).

RULE#1: Never, ever, no matter how "old-school" your rendering techniques are, use "shadow color" or "shadow density" settings. Ever. Trust me on this.

Enter "Ambient" light

"But", these early CG people said, "outdoors shadows from the sun is slighlty blue, shouldn't I set a shadow density and color to get my blue shadows"?

NO!!

The reason "shadows are blue" is because they are filled in by blue light from the sky.

Now, our early CG pioneers understood this, of course, so rather than the horrendeos hack of "shadow color", they introduced a nearly-as-horrendous hack: Ambient Light.

But the problem was, this "Ambient Light" was ever-present and uniform, and yielded a totally unrealistic and unsatisfactory result when used on it's own, something like this:

That looks about as horrible as the original: Sure, you can see something in the shadows - but it's all totally uniformly lit. The "legs" of our table can now be seen... but as totally uniformly colored blobs, with nothing to reveal their shape.

Are these round legs, or are they flat oval things, or what are those? Does the legs touch the floor, or are they hovering above it? The purple teapot looks almost flying, because the shadow behind the green teapot is just a flat color.

The problem here is that light is hitting every point uniformly, with no regard to the position or angle of the surfaces. But if we are trying so simulate "blueish light from the sky", then a point that is exposed to a lot of the sky will receive more light, than a point that is beind a bunch of other objects that are blocking (i.e. "occluding") the skylight.

Enter "Occlusion"

Luckily, some bright people at ILM back in 2002 when they were working on "Pearl Harbor" invented (using mental ray, I should add) something called "Ambient Occlusion". Basically, they wrote a shader that figure out how "occluded" a certain point was, i.e. how much stuff was "blocking light from arriving" at that point. This "Occlusion" on it's own looks like this:

Combining "Ambient" and "Occusion"

Now, if you apply this to the Ambient term, you get this very much nicer image:

See how beautifully the details resolve; the legs of the table now correclty reads as "contacting" the floor; the shape of the legs can be perceived. The area between the teapots is properly darkened, and the teapots have nice contact shadows.

The above is how it should be done!

Doing it the WRONG way

However, unfortunatly, many people have read and misunderstood the original ILM documents on Ambient Occlusion, and apply the Occlusion pass across the entire rendering. This is W R O N G!!

I.e. people make "plain" render (including ambient light and everything), make an occlusion pass, and just multiply the two in post!

The result is that you get a deceptively-sort-of-okay-but-somwhat-wrong looking result like this:

Notice how this has a "dirty" feel. This is because the occlusion pass (pictured above) was applied on top of the entire image, affecing the "ambient" light as well as the directional light.

But this makes no sense; the "occlusion" of the directional light is already taken into account - that's what the shadow of the light is. Ambient occlusion isn't called "ambient occlusion" for no reason; it's supposed to be applied to the "ambient" term, i.e. the "omnidirectional surrounding light", not to any direct lights.

But in the above image you will see darkening on floor in front of the objects, making it appear "dirty". Similarly, there is a bad looking "dirt-shadow" of the teapots spout on the front of the teapots. And so on.

SO: Globally multiplying occlusion on top of the beauty pass (including reflections, direct light, etc) is WRONG. Don't do it.

But isn't this all fake? Why are we doing it?

Now... all we are doing with our "ambient" light and the "occlusion" is simulating "omnipresent light" (i.e. light from the environment) as well as "bounce light" (from other objects). Lets compare the result with actually calculating omnipresent light and bounce light; i.e. use Final Gathering and calculate it FOR REAL:

The above image uses FG and a 3ds Max "Skylight" (i.e. light from the environment in XSI or Maya) to introduce the same kind of light we tried to "fake" with the "ambient" light - but correctly. And with true indirect bounces!

So this results begs the question; when we so easily can get the correct result, why would we still want to go the "fake" route?

There are a couple of answers:

FG is an interpolated technique. This means that the indirect lighting is sub-sampled (calculated less than for every pixel) and the values between those are interpolated. However, if you are doing an animation, and the result between two frames are slightly different (for whatever reason), this may - hypothetically - cause not one pixel to change, but a large area of pixels to change (i.e. all pixels influenced by the interpolation of that FG point).

The result, in a final animation, will be visible flicker. Visible, because it is "macroscopic", i.e. larger than a pixel, and perceived as "scintillation" or "flicker", which is visually unappealing.

Contrast this with using the occlusion technique: It is calculated for every pixel (every sample, even), and hence, any noise in this calculation is of sub-pixel size. I.e. a difference from one frame or another will only affect at most one pixel, and mostly just a fragment of a pixel.

The result is that this perceived more as "film grain", and is much less visually objectionable.
We may actually want to combine both "real" and "fake"; this is a method I often advocate.

You use FG at a low density and with high interpolation, and you apply your occlusion on top of this indirect light, rather than some homemade, arbitrarily invented "ambient" light. This relieves you of the responsibility of having to figure out the proper intensity and color of this mythical "ambient light" - it is calculated for you.

And of course, this combo method is a built in as a feature in Arch&Design/mia_material...

PRACTICE: How do we actually do this?

Since the original questions was in a 3ds Max context, I will answer (for now) in a 3ds Max context, but also mention the methods for XSI and Maya in the text.

There are three basic methods to apply ambient light:

Use the built in AO of Arch&Design/mia_material and utilize it's "Ambient" parameter
Use a light set to "Ambient Only"
Use a light with the Ambient/Reflective Occlusion shader as light shader.

Method #1: Arch&Design (mia_material) ambience

This method allows you either per-material or global ambient light levels, and you can easily modify the ambient occlusion radius from the rollout:

Open the material in the material editor
Go to the "Special Effects" rollout.
Turn on the "Ambient Occlusion" and...
- ...EITHER put in a given ambient light color in the material...
- ...OR: switch to the "global" mode, which will use the "ambient" color and intensity from the Environment dialog box:

In XSI and Maya this means enabling the built in AO of mia_material, and setting the "ao_ambient" parameter to the color of your desired ambient light.

Method #2: "Ambient Only" light

(AFAIK, this specific method only works in 3ds Max. Correct me if I am wrong.)

Create an Omni
In it's Advanced rollout, set the light to "Ambient Only"

This gives you plain (flat) ambient light with no occlusion.

To get the occlusion effect by adding the Ambient/Reflective Occlusion shader as the "Projector Map" of the light.

BUT - There is a big BUT - For this to work, you MUST have the light with it's transformation reset, i.e. it must be placed at 0,0,0 in the top viewport, or the ambient occlusion shader will be confused.

Doing this manually is tricky; so it can be done much easier with a script:


myLight = Omnilight() 
myLight.AmbientOnly = true 
myLight.projectorMap = Ambient_Reflective_Occlusion__3dsmax()

To run this script:

Go to MaxScript menu
choose "New Script"
paste the above snippet in
hit CTRL-E

You will now have a set up light, where you can modify it's intensity and color etc. w. the normal 3ds max light features. The only thing you need to look out for is if you wan to set the distance for the ambient occlusion rays, you must

take the Ambient/Reflective Occlusion shader that is in the projector map
drag-and-drop it into the material editor
choose "Instance"
...and modify the settings from the material editor

Method #3: "Ambient Only" light w. occlusion shader as light shader

There is actually a Method#3 which is similar to Method #2, except rather than placing the Ambient/Reflective Occlusion shader in the "Projection Map" slot, you use that shader as the light shader of the light itself.

A quirk of this methods is that now the shader completely replaces all the settings of the light; all controls for color, intensity, etc. stop working, and you need to do all changes to the light intensity and color by modifying the color of the "bright" slot of the occlusion shader itself (by putting it in material editor, as above).

This method has the benefit of not requiring the strange "light has to be in 0,0,0" requirement, plus that it is a method that works as well in Maya and XSI. To do this in XSI or Maya:

Create an area light
Set it's area light type to "User" and 1 sample
Use the mib_amb_occlusion shader as the light shader of the light

Similar to 3ds Max, changes to the "ambient light level" will now have to be done entirely from inside the occlusion shader.

Hope this helps.

Mo' later.

/Z

White Out - those nice "product renders"

2008-09-18T09:52:00.005+02:00

Here's a short tip: Did you ever want to be just like Apple? And render your products in a shiny magically white room, which still projects those nice magically faded reflections on the white surface?

To do this "physically real" is suprisingly tricky; you'll have all sorts of issues with the "white" actually either blowing out to superwhites, or the "white" in your reflections on the floor plane not looking "white enough" and if it does look "white enough" you can't just get that nice "faded reflection" look?

Well, here's where the production shaders can help you. Generally, you use the production shaders (specifically, mip_matteshadow) to apply differential shading to a background plate. I.e. if nothing is in shadow and nothing is reflected in the surface, the color returned is exactly the color you put in. Only when shadow falls is it darker, and if an object is reflected is the color actually touched.

But nobody said the background plate has to be a shot of your backyard. It can just be... well... plain old "white".

In this scene, the "floor plane" is using mip_matteshadow with a plain white color. The scene background is set to white. Traditional lights are used to light up the "CG objects" with traditional non-physical 0-1 intensity ranges. The reflections in the mip_matteshadow material is set to be subtractive, and to fade out over a given distance.

Et voila - you get this nice kind of render that you are used to finding on something like Apple store. Naturally, you can utilize the various Ray Switchers in the production library to allow the reflections in the objects to appear differently (i.e. a HDRI environment or somesuch) while the background still is just "white".

/Z

Blur Cinematic update

2008-09-05T10:07:00.004+02:00

A short update: There is a very cool thread over at ZBrush Central about the Blur Warhammer Cinematic mentioned in previous post, which is well worth a read.

On the topic of "random interesting links", I found this page oddly compelling; about a russian guy who invented a color photography process 100 years ago, and only now are the images actually - through the magic of computers - viewable again.

/Z

Blur goes "mental"

2008-08-24T11:56:00.002+02:00

Check out this new "Warhammer: Age of Reckoning" cinematic the insanely talanted guys at Blur Studios did:

It's done in mental ray (except some certain passes like particle work done in 3ds Max Scanline renderer (& maybe other renderers as well*)), and I even had the opportunity to render some of these characters myself, which was fun.

It's a suitably epic piece of work, I'd say.

What may interest people is that this is largely lit by physical sun&sky, and is using final gathering for indirect light. Clearly, the era of "fake everything" and "you can't use GI in production" is coming to a much needed close.

/Z

* = A ton of Particle work was done in FumeFX, which isn't available for mental ray quite yet. But a little bird has told me that this isn't too far into the future....

The Post SIGGRAPH 2008 Post

2008-08-21T16:02:00.005+02:00

Aaah, another SIGGRAPH done. This year was busier than ever, with both a course, masterclass and... stuff.

I'm still Jetlagged out of my head, even a week later, so this will just be a short post to say "I survived"... even the Blur party. :)

As you noticed (in previous post) the amount of QiK coverage I was able to do from the show was near nil - this was mostly due to lack of time but also rather shaky WiFi connectivity in the exhibition hall (it was fine in the conference areas, but who wants to see corridors? ;) ).

I must, however, take this opportunity to thank the guys of mymentalray.com who extended their hospitality quite extraordinarily to make me feel at home, especially Juan who gave me a little "tour".

mymentalray.com Maestro and Myself

While I was there I also visited my friends Colin & Greg at Hydraulx, in their new facility which I hadn't seen before. Verrry nice, their new screening room is sweeeeeeeeeeet. Me want ;)

Hydraulx screening room

/Z

Leaving, on a jet plane....

2008-08-09T08:30:00.007+02:00

So I'm pretty much at the airport, about to embark on the god-knows-how-many-hours flight to L.A, arriving, nice and toally jetlagged out of my head at about 4 PM saturday.

More stuff on Twitter & Qik, and sometimes I may appearn int he "fring" thingamabob on the right. Maybe. If that works. Who knows w. technology. :)

/Z

mrMaterials.com & The Floze Tutorials

2008-08-01T08:54:00.009+02:00

mrMaterials.com

Last week, the site mrmaterials.com opened officially to the public, so you can actually up- and download materials there as well as (like I mentioned in my last post) mymentalray.com. So don't be shy, up & download those nice mental ray materials as much as you like!

The Floze Tutorials

Florian Wild, most known as "Floze" online, has put together an outstanding set of tutorials for mental ray about rendering various types of environments. These are, in order:

Sunny Afternoon

Florian has undoubtedly done a great job on these, and they are very good reading, and even though they are written for Maya, mental ray is mental ray, so the basic techniques can be transported to XSI, 3ds Max etc. just as well.

Luckily, Floze has already done the thinking for you here as well, and this is available in eBook format from www.3dTotal.com for £8.55 (which I think he is well worth).

Enjoy

Stuff

Siggraph is closing in. I plan to do a bit of "reporting" from it on twitter, (so follow me there), and I may even, if I get extra crazy, do some QiK coverage. We'll see....

...until next time - keep tracing. ;)

/Z

Layer all your Love on Me, MyMentalRay, Material Libraries and.... Stuff

2008-06-27T13:15:00.012+02:00

MyMentalRay.com

First, before I start todays post, I advise everyone to run over to the freshly updated mymentalray.com which has a brand new fresh coat of paint, an updated material library, dynamic content, and a lot of other spiffy stuff.

Take note especially at the start of the mental ray material library over there. It's not the only effort of it's kind. My pal Jeff Patton is involved with a second very similar effort known as mrmaterials.com.

Simple Layering

I keep getting questions about layring (probably sparked by the recent writings about Iron Man) where you want to use something like Arch&Design (mia_material) to give both a broad specular glossy highlight, and a 2nd layer of a much more shiny "clearcoat" style material.

Well, nothing is stopping you from doing exactly that. I made this Iron Man material (apologies in advance to Ben Snow, and to all you guys for my lack of modelling sKiLz :) )

This isn't high art, but is there to demonstrate the concept. In most applications like Maya and XSI, you can easily blend materials using various blending nodes. But I did this in 3ds Max, and it's a little bit more difficult in a sense. I used the 3ds Max Blend material for this.

The trick is to understand that the 3ds Max Blend doesn't just *add* two materials (that's what the Shellac does), but it interpolates between them. This is generally better, because you do not break any energy conservation laws! (Also it works with photons that way!). Shellac, while nice, makes it really easy to make nonphysical materials.

However, since you are working with Blend you will have to take this into account. Here is an example:

From left to right:

Left: A completely mirroring Arch&Design material
Center: A glossy Arch&Design material in "Metal" mode
Right: a Blend material using the above two and a Falloff in Fresnel mode as the blend map.

A couple of things to note about this:

The "common mistake" people do is to make one material that is a shiny material with a falloff for the clearcoat, and completely reflective (glossy) material for the "base" material, and then try to blend these two with Shellac.

This very easily causes nonphysical reasults on edges. Instead doing a Blend between 100% reflective and the "base surface" makes sure to keep the energy in check.
Note that for metallic colored objects, their color does affect the color of reflection, but for dielectric objects the reflection is always white.

You do this by having the "Metal" mode turned on for the base objects (so reflection color is taken from diffuse color) but OFF for the clearcoat (which is a dielectric). This way you get the proper "uncolored" sharp reflections on top of "colored" glossy reflections.

In this particular "Iron Man" material, I also utilized pieces of the car paint shader to get the "flakes" (although the movie version didn't really have any) in the paint. For that I only utilized a single component of car paint (flakes) and had pretty much everything else coming from Arch&Design. For this reason I did use Shellac to layer the car paint with the Arch&Design.

More advanced Layering

This "Blend" technique can be used in multiple layers, witness this (again apologies for my modelling skills :) )

This image originated from a question I got about making "greasy brass", so I made this material (also available on mymentalray.com) which doesn't just blend two things together, but several. Without going too deep into the technique, I am blending between the metal layer, and two different "grease" layers, here with different bump maps.

The trick to keep straight in your head is to make each "layer" look as if it was only made of the given sub-material, and let the blending between the layers handle the weighting (and, unless you "know what you are doing", avoid blendings where they sum up to more than 100%. This is automatic in 3ds Max when using "Blend" but in Maya or XSI - or in 3ds Max when using "Shellac" - it's easy to run amok with the levels)

As always with metal, having something interesting to reflect (i.e. some HDRI environment or similar). But I covered that in an earlier episode (see also here about glossy materials).

...and Other Stuff(tm)

In other news:

On popular demand I updated the new skinplus.mi file mentioned in a previous post so it now has a special version that does displacement. See the (updated) post.
For those who has missed it, go over to FXGuide.com where there is lots of cool coverage of the vfx business. Also, if you aren't subscribing to CineFex, well, then you should.

Thanks for listening. As always, following me on Twitter is a great idea, especially as SIGGRAPH draws closer. I'll be Tweeting my location regularly while in L.A.

/Z

SIGGRAPH 2008 talks

2008-05-08T11:04:00.006+02:00

Phew. I just finalized the course notes for my SIGGRAPH talks.

As mentioned before, I will be holding an Autodesk masterclass with the title of "Miracles and Magic: mental ray technology in Photo-real Rendering for Production". This will - on popular demand - be a lot about gamma and linear workflow (I actually clocked the pure presentation "talky" part on this segment alone at 30 minutes, sans practical demo bit!).

Beyond the LWF/Gamma stuff, it'll talk about CG/Live Action integration, and tips for rendering flicker-free animations, and some other stuff (assuming I can get through it all in time ;) ).

Unless things change, the masterclass itself is from 1:30PM to 3:00PM on Thursday, August 14:th. There is also a "QA with all the masterclass presenters" on Wednesday, August 13:th at 9:00AM that I will also participate in. The full agenda and more info is here.

Furthermore, I will also be co-teaching a SIGGRAPH course entitle "HDRI for Artists" together with Kirt Witte (Savannah College), Hilmar Koch (ILM), Gary Davis (Autodesk) and Christian Bloch (HDRLabs).

The class is set for Monday, 8:30-12:15 in room 502A.

To make it easier to track these things, I've added a twitter feed, plus I gave this place a new, short, easy-to-remember URL:

www.mentalraytips.com

Enjoy.

/Z

Beauty isn't only Skin Deep: combining fast SSS with mia_material (A&D)

2008-04-24T12:13:00.013+02:00

UPDATE 2008-06-27: The file is now updated to support also support displacement in a new 'SSS Fast Skin+ (w. Disp)' material

UPDATE 2011-02-04: This is now updated with correct paths for 2011 versions

The image on the right is by Jonas Thörnqvist, an increadibly talented 3d Artist, and it is created using the mental ray skin shader.

Seeing some recent work from Jonas reminded me that I made some promises back in the day in this blog about tips on how to combine the "fast SSS skin" shader with the nice glossy reflective capabilities of the mia_material (i.e. "Arch&Design" in 3ds Max speak).

The trick w. the skin shader is that it uses light mapping. So the "material" that uses it must connect both a "surface shader" (the one which creates the actual shading) and a "lightmapping shader" (which is what pre-bakes the irradiance to scatter).

This is a tad tricky to do manually, and for this reason the skin shader is supplied as what is called in mental ray parlance a "material phenomenon". Well, suffice to say... it does all the magic for you! You don't need to think.

However, in some applications (notably Maya) this is different, and the skin shader comes shipped as a separate light mapping node and shader node, and there are scripts set up to combine them. Similarily for XSI, there exists a "split" solution already.

But the poor Max users are left behind. Like tears in the rain.

This is because a "material phenomenon" can't easily be combined with other things... coz it's a "whole complete package". And due to the peculiar requirements of the skin shader, it will not work if it is a "child" of some other material (like a Blend material in 3ds Max, or similar). So it's a wee bit hard to do from the UI.

However, what is not hard to do, is to actually write a different Phenomenon! As a matter of fact it is so simple, that I thought people would hop about doing exactly that left right and center. And indeed, Jonas, mentioned above, done exactly that. Which is why his renders are so cool.

It so happens I've had a modified version of the skin phenomena cluttering my harddisk for some time now... I just havn't gotten around to posting it before.

So, without further ado, here it is. It's experimental. It's unofficial. It's unsupported. If it makes your computer explode, so be it. Don't say I didn't warn you. Making no promises it even works. Etc.

Take the file skinplus.mi and save in your 3ds Max mental ray shader include autoload directory, i.e. it's generally something like:

For 3ds Max versions 2010 or earlier:

c:\Program Files\Autodesk\3ds Max ????\mentalray\shaders_autoload\include\

For 3ds Max versions 2011 or later:

c:\Program Files\Autodesk\3ds Max ????\mentalimages\shaders_autoload\mentalray\include\

Just put the file there, start Max, and you'll have a new "SSS Fast Skin+" and a "SSS Fast Skin+ (w. Disp)" among your materials. From there on it should be fairly self-explanatory. I hope.Have fun./ZJonas "Incredible Hulk"

3ds Max 2009 released: mr Proxies and Other Fun Stuff

2008-04-18T10:51:00.005+02:00

You may not have noticed, but a new release of 3ds Max has seen the light of day, known as "3ds Max 2009" (+/- a "Design" suffix).

"What, already?" I hear you ask. Yeah - indeed. This was a shortened development cycle to realign the release date of 3ds Max with other Autodesk products. Disregarding the marketing talk, it means that stuff had to happen in six months that normally takes a year. And being heavily involved in this release, I can say that I am still sweating from the workload....

For mental ray nuts such as yourself, there's some fun new stuff in 2009. Perhaps, most notably, is the hotly requested "mental ray proxies".

What is a "mental ray proxy", you ask?

mental ray proxies

Well, technically, it's a render-time demand-loaded piece of geometry. The particular implementation chosen for 3ds Max is in the form of a binary proxy. This means that the mental ray render geometry data is simply dumped to disk as a blob of bytes together with a bounding box. These bytes can then be read in... but not until a ray actually touches the bounding box!

Normally, geometry lives in the 3ds Max scene, and is then translated to mental ray data. So it means the object effectively lives twice in memory, once in 3ds Max, and once as the mental ray "counterpart". Not only does the proxies remove the translation time, it actually removes the need for the object to exist in all it's glory in 3ds Max; there is only a lightweight representation of the object in the scene, that can be displayed as a sparse point cloud so you can "sort of see what it is", and work the scene at interactive rates. Not until the object is actually needed for render is it even loaded into memory, and when it is no longer needed, it can be unloaded again to make room for other data.

One neat feature with the proxies is that they can be animated, i.e. mesh deformations can be stored (you can naturally just move the instances themselves around normally without having to save them as "animated" proxies, as a matter of fact, instance transformation is not baked into the file, only the deformations).

You can think of it as a point-cache on stereoids, because the entire mesh is actually saved - which means that topology changing animation (such as, say, a fluid sim) can be baked to proxies. Naturally, it'll eat lots of disk ... but it's possible. The animation can be re-timed and ping-pong'ed (so you can make, say, swaying trees more easily).

Making proxies

Now, creating proxies in the shipping 3ds Max 2009 is a bit of a multi-step process. I wrote a little script to simplify that, but it wasn't ready in time to make it into the shipping 2009, so you can find it here:

Download mental ray-mrProxyMake.mcr
Launch max, and on the MaxScript menu choose "Run Script" and pick the file. By doing this, it should now have installed itself.
Now open your "Customize" memory, the "Customize User Interface"
Choose the "Quads" tab
On the left, choose the category "mental ray"
In the list that appears, you'll find a "Convert Object(s) to mental ray Proxy". Make sure the one with the plural "s" on "Object(s)", if you find one without s it is the shipping one which is not so fun. ;)
Drag it to a quad menu of your choice - done!

Now you should be able to right-click an object, and get a "Convert Object(s) to mental ray Proxy" option.

This allows you to convert an object and replace the original with a mr Proxy. Note this removes your original, replaces it (and all it's instances) with the proxy. It retains all transformation animation, children and parent links in all the instances. Now be aware your original is thrown away - do don't do this on some file which you do not have a saved copy of your carefully crafted object!!!

You can also select multiple objects for baking to proxies. This, however, works slightly differently. Instead of just a filename, you are asked for a file prefix, and the actual object name in the scene is then appended to that name.... so if your prefix is "bob", then "Sphere01" is saved as "bobSphere01.mib".

Disclaimer

Now, this is an unsupported experimental tool. Be aware it will delete your original Object(s) - so save your original scene. It may have a gazillion of bugs, misfeatures, and may cause your computer to explode. There is no warranty that it'll even execute. But if you find it useful.... enjoy. ;)

What about particles? Pflow?

Now the next question I invariably get is this: Can you instantiate proxies as particles? I doesn't seem to work?

The story is this. Back in the day, 3ds Max had issues with handling many objects. Many polygons was easier for it to handle. And even today, I guess a million single-polygon objects will be much slower than a single million-polygon object, due to the per-object overhead.

Many (if not all) the 3ds Max tools, including particle systems, were written with this in mind. So, for example, instantiating an object into a particle system means that the mesh itself is copied. So when you have a box, and instantiate this into a particle system w. 1000 particles, this doesn't really make 1000 boxes. It actually makes a single mesh containing the faces copied off the 1000 boxes.

Since the mr Proxies aren't meshes (they have no geometry as seen from inside max, they are helpers), they can't be copied as meshes. It won't work!

Luckily, the planet is filled with Smart People. One of these Smart People is named Borislav "Bobo" Petrov, and if you've ever used a MaxScript, you've heard of him.

Naturally, Bobo has a solution. Check out this post on CGTalk, where Bobo posts a script which can bake any scene instance to a particle flow particle system.

The script creates real and true instances of the objects, rather than trying to "steal the mesh faces". And by virtue of doing true instances, it works perfectly with the mr Proxies.

I honestly have no idea what the 3ds Max community would even do without Bobo, he's such a phenomenal resource.

So, there you go. Have fun with 3ds Max 2009 and PFlow'in your proxies....

/Z

Visual F/X tip: Blowin' Stuff Up

2008-04-04T14:20:00.003+02:00

I just had to post this, coz' it's so useful. It's got nuttin' to do with mental ray, but hey, I like it, so I post it.... and you, dear reader, may very well be into visual effects, so....

Here's the thing:

My very good friend and certified "madman" Bob Forward has a site dedicated to downloadable stock pyro footage called Detonation Films.

I've used Bobs stuff in the past, I stumbled there recently and saw that not only has Bob upgraded to HD for a lot of his effects, he has lots more than I ever saw before!

There's explosions, explosions, bullet hits and explosions. There's blood, sweat, and tears. There's debris, theres smoke, there's fire.... there's perdy much anything you'd need, and all available for electronic purchase (w. a lot of cool freebies too)!

And there's also Kabumei, and Bob's other films....

Yes, this man is insane; he lives to blow stuff up, but he is sane enough to keep a camera nearby every time he does it...

So.... I just thought I'd throw Bob a plug, "just coz". And no, he ain't paying me for saying this (although that's an idea... ;) )

/Z

Quick Informal Poll on Gamma Stuff

2008-03-24T14:01:00.007+01:00

"Sponza Overgrown" (more here)

A discussion recently came up on CGTalk about gamma correction.

Since I have an Autodesk Masterclass at SigGRAPH 2008 which touches briefly on the subject, I was thinking if I should, by "popular vote", actually expand that section of the masterclass, perhaps shave off some other things and talk more about Gamma?

Technically, the agenda is already "set" but I could perhaps be flexible?

What do you think? Do you plan to go to SigGRAPH 2008 in L.A.? Would you attend the Masterclass, and if so, would you want to hear more about Gamma stuff? Or would you rather hear about the other things?

Please post a reply to this blog post with your preference.

To be clear: This question is about SigGRAPH in particular. Gamma is a topic I'll be adressing quite a lot here, to the point of making a whole website about it. So it's not like there will be any shortage of online info.

(Btw, I also co-teach on a "HDRI-for-artists" SigGRAPH course)

/Z

Why does mental ray Render (my background) Black? Undestanding the new Physical Scale settings

2008-02-19T13:30:00.007+01:00

The most common "complaints" I get about mental ray rendering in 3ds Max 2008 is "it's washed out" and "it Renders black". The answer to the former is "you are not handling your gamma correctly", and will be thorougly covered in the future. The answer to the latter is "You are not understanding the Physical Scale" settings. Which is what we're going to talk about now.

Color and Color

Without going too deep into the physics of photometric units (we did that already) we must understand that a normal color, an RGB value, i.e. a pixel color of some sort, can, fundamentally represent one of two different things:

A reflectance value
A luminance (radiance) measurement

The "luminance" of something is simply how bright it looks. It's probably the most intuitively understandable lighting unit. Basically, you can say that when you are looking at the pixels your digital camera spit out on your computer, you are looking at pixels as individual luminance measurements, converted back to luminance variations by your screen.

I.e. a given luminance of some real world object flows in through the lens of your camera, hits the imaging surface (generally a CCD of some kind) and gets converted to some value. This value (for the moment ignoring things like transfer curves, gamma, spectral responses and whatnot) is, in principle, proportional to the luminance of the pixel.

Now "reflectance" is how much something reflects. It is often also treated in computer graphics as a "color". Your "diffuse color" is really a "diffuse reflectance". It's not really a pixel value (i.e. a "luminance") until you throw some light at it to reflect.

And herein lies the problem; traditionally, computer graphics has been very lax with treating luminance and reflectance as interchangeable properties, and it's gotten away with this because it has ignored "exposure", and instead played with light intensity. You can tell you are working with "oldschool" rendering if your lights is of intensities like "1.0" or "0.2" or something like that, in some vague, unit-less property.

So when working "oldschool" style, if you took an image (some photo of a house, for example) and applied as a "background", this image was just piped through as is, black was black, white was white, and the pixels came through as before. Piece of cake.

Also, if you took a light of intensity "1.0" that shone perpendicular on a diffuse texture map (some photo of wood, I gather) will yield exactly those pixels back in the final render.

Basically, the wood "photo" was treated as "reflectance", which was then lit with something arbitrary ("1.0") and treated on screen as luminance. The house photo, however, was treated as luminance values directly.

But here's the problem: Reflectance is inherently limited in range from 0.0 to 1.0... i.e. a surface can never reflect more than 100% of the light it receives (ignoring fluorescence, bioluminescence, or other self-emissive properties), whereas actual real-world luminance knows no such bounds.

Now consider a photograph... a real, hardcopy, printed photograph. It actually reflects the light you shine on it. You can't watch a photograph in the dark. So what a camera does is to take values that are luminances, take it through some form of exposure (using different electronic gains, chemical responses, irises to block light, and modulating the amount of time the imaging surfaces is subjected to the available luminances). Basically, what the camera does, is to take a large range (0-to-infinity, pretty much) and convert it down to a low rang (0-to-1, pretty much).

When this is printed as a hardcopy, it indeed is basically converting luminances, via exposure, into a reflectance (of the hardcopy paper). But this is just a representation. How bright (actual luminance) the "white" part of the photographic hardcopy will be depends on how much light you shine on the photograph when you view it - just like how bright (actual lumiance) the "white" part of the softcopy viewed on the computer depends on the brighness knob of the monitor, the monitors available emissive power, etc.

The funny thing with the human visual system is that it is really adaptive, and can view this image and fully understand and decode the picture even though the absolute luminance of the "white" part of the image varies like that. Our eyes are really adaptive things. Spiffy, cool things.

So, the flow of data is:

Actual luminance in the scene (world)
going through lens/film/imaging surface and is "exposed" (by the various camera attributes) and
becomes a low dynamic range representation on the screen, going from 0-to-1 (i.e. from 0% to 100% at whatever max brightness the monitor may have for the day).

So, now the problem.

In the oldschool world we could draw a near equivalence between the "reflectance" interpretation and the "luminance" interpretation of a color. Our "photo of wood" texture looked the same as "photo of house" background.

What if we use a physical interpretation?

What about our "photo of wood"? Well, if we ignore the detail of the absolute reflectance not necessarily being correct due to us not knowing the exposure or lighting whtn the "photo of wood" being taken, it is still a rather useful way to reperesent wood reflectance.

So, if we shine some 1000's of lux of light onto a completely white surface, and expose the camera such that this turns into a perfectly white (without over-exposure) pixel on the screen, then applying this "photo of wood" as a texture map will yeild exactly the same result as the "oldschool" method. Basically, our camera exposure simply counter-acted the absolute luminance introduced by the light intensity.

So, in short, the "photo of wood" used interpreted as "reflectance" still works fine (well, no less "fine" than before).

What about us placing our "photo of house" as the background?

Well, now things start to change... we threw some thousands of lux onto the photo, creating a luminance likely in the thousands as well.... these values "in the thousands" was then converted to a range from black-to-white by the exposure.

So what happens with our "photo of house"? Nothing has told it to be anything than a 0-to-1 range thing. Basically, if interpreted strictly as luminance values, the exposure we are using (the one converting something in the thousands to white) will covert something in the range of 0-1 to.... pitch black. It won't even be enough to wiggle the lowest bit on your graphics card.

You will see nothing. Nada. Zip. BLACKNESS!

So, assuming you interpret oldschool "0-to-1" values directly as luminance, you will (for most common exposures) not see anything.

Now this is the default behaviour of the mr Photographic Exposure control!!

This setting (pictured above) from the mr Photographic Exposure will interpret any "oldschool" value directly as a cd/m^2 measurement. And will, with most useful exposures used for most scenes, result in the value "1" representing anything from complete blackness to near-imperceptible-near-blackness.

(I admit, I've considered many a time that making this mode the default was perhaps not the best choice)

So how do we fix it

Simple. There are two routes to take:

Simply "know what you are doing" and take into account that you need to apply the "luminance" interpretation at certain points, and scale the values accordingly.
Play with the "Physical Scale" setting

Both of these methods equate to roughly the same result, but the former is a bit more "controlled". I.e. for a "background photo" you will need to boost it's intensity to be in the range of the "thousands" that may be necessary to show up for your current exposure. In the Output rollout, turn up "RGB Level" very high.

Of course, in an ideal world you would have your background photo taken at a known exposure, or where you had measured the luminance of some known surface in the photo, and you would set the scaling accordingly. Or even better, your background image is already a HDR image calibrated directly in cd/m^2.

But what of the other method?

Undersanding the 'Physical Scale' in 3ds Max

When you are using the mr Phogographic Exposure control, and you switch to the "Unitless" mode...

...one can say that this parameter now is a "scale factor" between any "oldschool" value and physical values. So you can think of it as if any non-photometric value (say, pixel values of a background image, or light intensities of non-photometric lights) were roughly multiplied by this value before being interpreted as physical values. (This, however, is a simplification; under the hood it actually does the opposite, it is the physical values that are scaled in relation to the "oldschool" values, but since the exposure control exactly "undoes" this in the opposite direction, the apparent practical result of this is that it seems to "scale" any oldschool-0-1 values)

When to use which mode

Which method to use is up to you. You may need to know a few things, though: The "cd/m^2" mode is a bit more controllable and exact. However, the "Unitless" mode is how the other Exposure controls, such as the Logarithmic, work by default. Hence, for a scene created with a logarithmic exposure, to get the same lighting balance between photometric things and "oldschool" things, you must use the unitless mode.

Furthermore, certain features of 3DS Max actually works incorrectly, indeed limiting their output to a "0-1" range. Notable here is many of the volumetric effects like fog. Hence, if the "cd/m^2 mode" is used, it blocks fog intensity to max out at "1 cd/m^2". This causes things like fog or volume light cones to appear black! That is bad.

Whereas in the "Unitless" mode, the value of "Physical Scale" basically defines how bright the "1.0" color "appears", and this gets around any limitation of the (unfortunately) clamping volume shaders.

BTW: I actually already covered this topic in an earlier post, but it seems that I needed to go into a bit more detail, since the question still arise quite often on various fora.

Hope this helps...

/Z

More Hidden Gems: mia_envblur - glossy reflections of Environments

2007-11-05T15:06:00.003+01:00

I thought initially I would title this post "Happiness is a Warm Gun", since it could have just as well have been the "black gun metal" tip, but I felt a more "searchable" name would be more useful...

Formulating The Problem

Glossy Reflections in computer graphics is always a headache, since it invariable involves multiple samples, which invariably involves grain. Interpolation helps, but interpolation isn't really working well for complex geometries, and can be "detectable" in animations (i.e. you can often "see" that something fishy is going on w. reflections, so I advice against using interpolated reflections in animations).

But, you say, I need to have my semi-glossy space robot/gunship/whatever and I need to animate it, and I have this really contrasty HDR environment it must reflect... I would need to turn up samples to crazy levels... the animation would never be finished! What can I do!?

The solution: mia_envblur

This shader is another "sort of hidden" (depending on which application you are running, it's hidden away in 3ds Max but not in Maya, and it's existence isn't really marketed heavily... ;) )

What does it do?

Well, the documentation explains this fairly clearly, but in short:

If you have some objects in a scene which largely reflects an environment map (this bit is important; mia_envblur really dosn't do anything useful for, say, an architectural interior where objects reflect other objects, it only does it's job for environment reflections) and your environment is high-contrast, you tend to get grain as a result. Witness here some spheres n' stuff reflecting the good old "Galileo's Tomb" probe from Paul Debevec:

Grusomely Grainy

This is clearly not satisfactory, the grain is very heavy, causing slow renders due to a lot of oversampling happening. We can turn up the sampling in the shaders and get something like this:

Borderline Better

This looks nicer indeed, but the render time was nearly ten times of the above! Not something you'd want to do for an extended animation. And it would still glitter and creep around. Not good.

So... enter mia_envblur. The shader is used to "wrap around" some existing environment shader, i.e. it takes some other environment shader, rasterizes it into an internal mipmap, and can perform intelligent filtered lookups in a special coordinate space which behaves very close to doing actual glossy lookups to that environment with a near-infinte amount of rays!

Soothingly Smooth!
This is much nicer looking, and the environment reflections are smooth (but object-to-object reflections still involve multi-sampling and can have some grain. A trick around that is to limit the reflection distance as mentioned in the manual).

To use mia_envblur, you must follow these steps:

Where your existing environment shader is connected, instead connect mia_envblur, and connect your original environment into it's environment input.
In your mia_material, turn on it's "single_env_sample" parameter. This is very important or you will gain neither speed nor quality (although you will get a little bit of smoothing, but not supersmoothing of the reflections)
Set the "resolution" high enough to resolve the details of your original environment.

As for the actual blur amount, you have two choices; Either you set a fixed amount of blur with the mia_envblur parameter Blur. But that is a bit boring... if you have different materials of different glossiness, you would need separate copies with different blur ammounts applies as environment maps to each materials... very tedious...!

Much better is to turn on the mia_material_blur parameter on!

This will drive the amount of blur from the glossiness setting of the mia_material. This works such, that mia_material "informs" the environment shader which glossiness is used for a certain environment lookup, and hence allows a single global copy of mia_envblur (applied in the global (camera) Environment slot) to follow the glossiness of multiple mia_materials, or even map-driven glossiness on a single material:

Very Visible Variable Varnishness

I can't stress enough how varying the glossiness with a map gives a nice feel of wear, tear and "fingerprintiness" of an object. And with mia_envblur you can do this without being ashamed and fear horrid render times.

Production Shaders?

Yes, mia_envblur works great together with the production shaders. Just "wrap" it around your mip_mirrorball shader, to do glossy lookups into it.

Perfect Production Partner

This spaceship (from TurboSquid) is mapped with a glossy reflection that is heavily varied (A whole "make a spaceship in the backyard" tutorial will probably appear later, if I find time).

Does it move?

Yes it does. Just a word of warning: be certain that the resolution parameter is set high enough to resolve all details in the environment you use. The "Gallileo" probe I use here has too many small lights in it for the default of "200" to be enough (this means the map is rasterized into a 200x200 pixel mipmap). But at 600 it works great. Also note that any non-glossy lookups into the environment map actually bypasses mia_envblur automatically, so these are looked up in the full resolution map!

See for yourself in this DivX test animation, which includes above spaceship hovering over my backyard, the above gun-metal-black battle robot (also from from TurboSquid) and some spheres, including my attempt to do a "gnarly cannon ball".

For the record, these renders also uses the photographic exposure and Lume "Glare" shader. The animations rendered at about 1 minute per frame (on a HP x6400 Quad Core)

Hope this helps your glossy-thing-renders!

/Z

Production Shader Examples

2007-10-30T15:18:00.001+01:00

So, who wants to know more about the production shaders? Raise of hands? (See the introductory post, if you missed that.)

OK, I don't have time for an extravagant essay right now, but what I did do is to put a set of examples online.

The example uses some geometry (in some cases, our friend "Robo" pictured here on the right) and shows how to use this together with the production shaders, both to introduce our geometry into various backgrounds, as well as using features like the motion blur and motion vector code.

General Overview

The Production library does a lot of things, but one of it's specialties is to help us to integrate a CG object into a photographic background, with the help of a photo of the background and a photo of a mirror ball taken at the same location in the same camera angle as the background photo. So, to play with that, we need a set of backgrounds, with matching mirror ball photos.

As luck would have it, I happen to have just that. (Amazing, innit?) ;)

These backgrounds are available in this backgrounds.zip file. Please download that and unzip before downloading any of the demos scenes (I also apologize for not having time to put Robo into any of the Maya scenes, but he was out at a party the day I made those file and didn't come home until late....)

In a hurry?

If you don't want to read, but play play play, you can go directly to this directory and you will find the files.

Examples for 3ds Max 2008

The 3ds Max demo scenes are sort of "all in one" demos, demonstrating a scene using the mip_matteshadow, mip_rayswitch_environment, mip_cameramap and mip_mirrorball to put a CG object into a real background as described in the PDF docs.

The file robot-1.max puts Robo in my back yard, robot-2.max puts him on my dining room table, robot-3.max on a window ledge, robot-4.max out in a gravel pit (how absolutely charming place to hang out) and finally robot-5.max on my dining room table but at night, and some alien globules has landed...

They all work pretty much the same, i.e. the same settings only swapping in different backgrounds and mirror ball photos from the backgrounds.zip file.

The exception is the file robot-4-alpha.max which demonstrates how to do the same as robot-4.max does, but set up for external compositing (see more details below in the Maya section).

Examples for Maya 2008

The examples for Maya are more "single task" examples, and demonstrates one thing at a time.

mip_matteshadow1.ma and mip_matteshadow2.ma both demonstrate how to put a set of CG objects into a real background, using the exact same techniques as for 3ds Max above:

The file mip_matteshadow2b.ma demonstrate the same scene as mip_matteshadow2 but set up for external compositing (what is called "Best of Both Worlds" in the manual).

To recap from the manual briefly: In the normal mode (when you composite directly in the rendering and get a final picture including the background right out of the renderer, you use mip_cameramap in the background slot of your mip_matteshadow material, and in your global environment (in the Camera in Maya, in the "Environment" dialog in 3ds Max) you put in a mip_rayswitch_environment, which is being fed the same mip_cameramap into it's background slot, but into it's environment slot it is being fed a mip_mirrorball.

To do the "Best of Both Worlds" mode (to get proper alpha for external compositing, and not see the background photo in the rendering - but yet see its effects, its bounce light, its lighting, its reflections, etc. - one need to do a couple of changes from the above setup:

In the global Environment should still be a mip_rayswitch_environment as before, the only difference is that instead of putting mip_cameramap into it's background slot, you put transparent black (0 0 0 0).

The trick in Maya is that you cannot put an alpha value into a color slot. We can cheat this by using the mib_color_alpha from the base shaders, and set its multiplier to 0.0.
In the background slot of your mip_matteshadow you used to have a mip_cameramap with your background. What you do instead, is to put in another mip_rayswitch_environment, and into it's environment slot (important, yes, the environment and NOT the background!) you put back the mip_cameramap with your background photo, and in it's background slot you again put transparent black (using same trick as above).

Having done this (as is already is set up in the mip_matteshadow2b.ma example) you will get this rendering:

This image contains all the reflections of the forest, the bounce light from the forest, the reflection of the environment from the mirror ball... but doesn't actually contain the background itself.

However, it has an alpha channel that looks like this...

...which as you see contains all the shadows. So compositing this image directly on top of the background in a compositing application, will give you the same result as the full image above, except with greater control of color balance etc. in post.

Maya in Motion

There is three further example files for Maya:

mip_motionblur.ma, which demonstrates the motion blur, and mip_motionvector.ma and mip_motionvector2.ma who both demonstrate how to output motion vectors.

I know these are rudimentary examples, but the day only has 48 hours... ;)

To quote the Governator: "I'll be bak".

/Z

Making Better Metal with mia_material

2007-10-30T12:31:00.000+01:00

When using the Arch&Design (mia_material) in the various products, the manual mentions that to make metal, one should enable the "refl_is_metal" switch (shown here from the 3ds Max UI, but it's available in all products):

Metal Mode

When one does so, the color of the metal comes from the diffuse color swatch. However, most people stop there, and get a very dull looking material, and wonder "what wen't wrong?".

Well, not reading the rest of the manual is what went wrong ;)

Just kidding. Anyway, just turning on the "metal" mode doesn't make it look magically like metal. It looks more metal-ish but there is one more thing to do, take care of the BRDF curve.

When metal mode is on, the reflectivity (and the BRDF curve) drives the balance between traditional "diffuse" shading and reflective "metallic" shading. So if your reflectivity is zero, or you are at an angle where the BRDF curve is very low, you will be seeing mostly plain old diffuse shading, i.e. not very "metal" looking.

So what needs to be done is to pump up the Reflectivity value (probably to 1.0), and modify the BRDF curve to contain more reflectivity.

The default BRDF curve only contains a 0 degree reflectivity of 0.2, which isn't really very "metallic looking". One could change this to a higher value like so: (UI from 3ds Max shown, but exists in all products):

Making Metal More Metallic

This works pretty nicely, and most metals can be done this way. But still, it may look a tad "off" in how the reflectivity depends on angle.

Well, then we try the fresnel mode.

"What" I hear you yell, "Fresnel" is for dielectrics... transparent stuff... like water, glass and such. It is based on the Index Of Refraction. Metals aren't transparent, they can't refract stuff! O'le Zap's gone completely bonkers now!

Well... actually... no. Metals are indeed not refractive, and are indeed not dielectrics (meaning, electrical insulators). They are Conductors, and for some baroque reason these are also considered to have an "Index of Refraction".

Now, don't ask me how on earth someone came up with the idea of refractive metals or how this is actually calculated... I didn't write the laws of Physics (I just abuse them) so just trust me it's there.... and these values are high. Not your average "1.3" ish like for water, but values like "25" or "50".

So, if you turn on the Fresnel reflection mode and put in an IOR of 50 you get something like this (Again UI from 3ds Max coz it has the neat curve):

Mysterious Metal Magic

As you see from the quirky curve, the angular dependency of the metallic reflection is... odd. But when rendering this, the metal just looks a tad more... well... metallic:

The above is a gold material under Sun&Sky lighting. It looks "ok", but not great.. why is that? Well, our visual perception of metals come largely from the reflections. While a totally empty sky is "ok" as reflection, it's not more than just "ok"... it looks dull. (But a photo of metal in a completely cloudless desert would look about as dull).

Lets try with reflecting the good o'le "Kitchen.hdr" environment:

There, exactly the same material, only reflecting something "interesting". (And yes, a tad of Glare on top, and using the Photographic exposure... so sue me ;) )

Hope this helps in the quest for More Metallic Metals.

/Z

Production Shaders: "Hidden Treasures" of 2008

2007-10-26T11:53:00.000+02:00

May I present to you, the "production" shader library.

What? Where? Production shaders?
Well, here's the story:

The Hidden Shaders

If you have installed 3ds Max or Maya 2008, you will have obtained mental ray 3.6, and with mental ray 3.6 comes the production shader library.

However, in neither of Max or Maya are these shaders exposed by default to the end user. They are hidden, and therefore "unsupported".

Still, they are there, and they can be used. But to do so, one must first "unhide" the shaders.

Why "hidden"

Simple matter of resources of Quality Assurance at Autodesk. The shaders has not gone through enough torture - yet - to be signed off by QA as "officially supported". But that's where you, my adventurous mental ray addict, come in! Consider this an extremely public beta, if you will....

How do I "unhide" them?

Unhide instructions for 3ds Max 2008 are here

Unhide instructions for Maya 2008 are here

What are they

The production shader library is a set of tools, some simple, some complex, to aid in doing production rendering, i.e. in a visual effects context.

There are two basic categories of shaders:

Simple
First we have the simple utilities like applying a gamma to a color, or giving different results for different "ray types" (reflection rays, transparency rays etc.). These shaders are very simple, and you probably have found similar shaders online before. These shaders are not better than those other shaders that do the same thing, they are simply a standard set that now ship with all products. I.e. "mip_rayswitch" isn't terribly different to Control Studio's "ctrl_rays", but you don't have to install anything to use it.

Advanced
Then we have the more complex shaders, such as the 2.5d motion blur shader, or the matte/shadow/reflection system used to cast shadows (and reflections) off of a stand-in object in your scene, for integrating CG objects into a background plate.

A lot of examples of the mip_matteshadow and other production shaders are available as a small demo movie constructed for siggraph, it's available as YouTube as well as WMV, QuickTime and DivX versions.

What do they do?

The main intent is to simplify the workflow of compositing CG objects into background plates, and other visual-effects related tasks that one may run in to on a daily basis.

In some cases they exist to give a simple workflow to a simple thing. For example, the mip_cameramap is a simple camera mapping shader that simply projects back an image from the render camera (and only that camera) "into" the scene 3-dimensionally (unlike, say, mib_lookup_background, Max's "Screen" mapping, or similar).

There are more complex "camera projection" shaders out there both for Maya and Max that can do similar jobs, but at a slightly higher effort. Again, the logic here is to provide the simple tool that can do the job, and if you need the more advanced feature, use the more advanced feature.

Similarily, the mip_mirrorball shader is for a simple unwrap of a mirror ball into an environment map when taken from the same camera angle as the background plate. For anything more advanced you would probably have to unwrap the mirror ball image in some unwrapping software and apply as a spherical map... or maybe you are a high-end user that uses SpherOn cameras and don't even use mirror balls... then ignore this shader, use your more powerful tools.

Mark my words, I will be posting quite a lot on the topic in the months to come, but meanwhile you can read the PDF documentation. In Max, the names of the shaders will appear slightly different than in the manual, but you can figure that our rather quickly, I hope.

That's all I have time for for for now:

Stay tuned to future blog posts on the subject.

/Z

Max 2008: Physical Camera with DOF and motion blur

2007-10-25T09:57:00.000+02:00

So, does anyone want a Physical Camera for mental ray in 3ds Max 2008? Read on...

The Photographic Exposure Control (mia_exposure_photographic) gives you values in f-stops and shutter speeds like in a real camera. However, it only applies to the exposure of the image (i.e. the brightness, basically).

In a real camera, the above mentioned parameters affect the depth of field and the motion blur of the camera.

This isn't supported out-of-the-box - the exposure control really only deals with the exposure.

A second thing is that the exposure knobs being "camera oriented", but they are not ON the actual Camera object. Whereas it would make more sense if these parameters "lived" in the UI of the Camera.

To try to solve these issues, I wrote a little "proof of concept" script to test out what such a UI would perhaps look like. It's very clumsy in many ways and an ugly hack, because it's just a "scriptable plugin", and scriptable plugins has a ton of limitations in max.

First of all, a scriptable plugin can only extend an existing object, not make a "new" one. Secondly, scriptable camera can only extend the "free" camera due to technical limitations of MaxScript (well, the MaxScript docs tell me so anyway), but most people "want" to use a "Target" camera.

Due to this limitation, the camera always gets created in "Free" mode, but after it has been created, you can switch it to "Target" mode. Ugly, but... livable.

How to use this plugin hack

1. Download this plugin and save into the "plugins" directory under your 3ds Max main directory.

2. Now, either restart max, or just load the plugin manually as well from the MaxScript menu.

3. Now, under your "cameras" you have a new "mr Camera" item.

4. Insert it - unfortunately always comes in as a "Free Camera". The UI at this point will look like the old camera.

5. Go to the "Modify" tab to see the "new" UI.

6. Play, rejoice, etc.

Remember, this is an ugly unsupported quick hack. The "mr Camera" simply "feeds" other existing plugins with value (mr Photographic Exposure, mental ray Depth of Field, motion blur, etc.) and doesn't really "do" anything by itself.

And it probably has more bugs than you can shake a stick at... but is provided here "for fun".

Enjoy.

/Z

"What he said"

2007-10-23T16:45:00.000+02:00

I love when people save me time. One guy who saves me time sometimes is Jeff Patton. He has another mental ray Blog an sometimes he reads my mind, and magically write things that I intend to post, saving me the time to actually post it.

Just now, for example, Jeff posted a tip on how you can use the portal lights as light cards. Quite useful, and quite an intended "additional feature" of the portal lights, albeit perhaps a tad under-documented....

Another cool mental ray Blog (more slanted towards Maya) is DJX blog with a lot of cool tips.

I'll add these blogs to my link list on the right, methinks....

/Z

3ds Max 2008 released: Some Known Issues

2007-10-23T09:44:00.000+02:00

Or "Why do my brand new 3ds Max 2008 render black when I choose a mental ray render preset"?

3ds Max 2008 has been released, and as always, some things sneak in the wasn't really intended in the final version.

Here, a "minor edit" to the rendering presets became less minor than was intended;

Since 3ds Max 2008 contains the new mr Photographic Exposure control, the rendering presets (y'know, the ones down at the bottom of the render dialog) for daylight was supposed to be changed from the old Log exposure to the new Photographic exposure set for "sunny day" lighting.

The problem? That this was done.... but by accident all mental ray render presets got this setting.

Yes, even the "plain old" settings got, by mistake, a setting suitable for a superbright sunny day enabled:

The setting accidentally put in

But a sunny day can easily be lit by 100000 lux. And your average interior surely is not. So out of the box, starting up max and putting in some photometric lights (try to use the photometric lights as often as possible, btw) you would get a really dark scene.

And even worse, putting in some non-photometric scene would yield a pretty much completely BLACK scene. Why?

Well, the new mr Photographic Exposure Control has a 2nd feature; The feature of treating any "oldschool" value as real, physical cd/m^2 values (if you wonder about what a "candela per square meter" is, go back to the "Gnomes and Basketballs" post).

The Units Setting

This means that if an "oldschool" light of the arbitrary intensity value "1.0" shines perpendicular to a white (100% reflective) lambertian surface (i.e. plain old white diffuse thingamabob), this will emit light that is interpreted as 1 cd/m^2.

Now that is really really really really REALLY really dark.

I.e. turning on max, loading a mental ray render preset, and putting in and oldschool "Omni" light gives you a black render. Not good.

The fix? Easy.

Do one of three things:

Either:

1: Turn it off altogether

Hit "8" to bring up the "Environment/Effects" dialog and do as follows:

Exposure Control Turned Off

By simply turning off the exposure control, you are back to a "known" behavior. However the exposure control is really neat and gives very nice images... so I don't really recommend that method!

2: Use the exposure controls "non physical" mode

Exposure Control in "Non Physical" mode

This is better; it still gives you all the nice image control of crushing blacks, taming highlights, camera vignetting and saturation controls, but it uses a fixed unity gain, i.e. the intensity of the pixels does not change (except it applies a gamma correction if the 3ds Max gamma is disabled, if the 3ds Max gamma is enabled, that gamma is used).

However, it is not perfect just because of the fact that you lack any control over exposure; the "non physical mode" is locked to unity gain with no control over it.

There is, however, a third variant:

3: Use the exposure control with an EV=0.0

Exposure Control with an EV of 0.0

It so happens that when using the "oldschool pixels equal cd/m^2 mode" (pictured above) the EV value of zero (0.0) is very close to the "unity gain" mode set by the "Non Physical" mode. But you can change it up or down to re-expose the scene.

So for a scene lit completely with "oldschool" lights (non photometric), that is the easiest setting with the greatest control.

A further note on the units / physical scale

Now if you have an old scene with a blend of photometric and non-photometric lights, you may want to revert to the old behavior of using the "physical scale" setting, which exists in the old Logarithmic exposure control.

Using a "Physical Scale" like in the past

In this mode you cannot use the "EV=0" setting, you probably need to pick one of the "indoor" presets, or just play with the EV until you get a "nice" image, because this means that now an oldschool light of intensity "1.0" will equate to an illuminance of ~1500 lux when perpendicular to a surface, so an exposure "suitable" for that amount of light must be used.

Hope this helps!

/Z

Yer in a "Heap" of trouble now: Avoiding random crashes in Maya/Max due to running out of Windows resources!

2007-10-14T07:59:00.000+02:00

Note; This tip has nothing to do with mental ray at all, but since the issue I describe tend to manifest on Maya when opening the mental ray control panel (due to the sheer number of tiny windows w. subwindows) I mention it here.

Have you ever run, for example, Maya (on Windows XP or earlier - Vista works better here) with a ton of other programs running, and tried to open a particularily complex AE template for some shader, to find the application go "plop" and disappear?

While there are any number of probable causes, I was debugging a particular case and actually found the cause, and it was sometihng I never really suspected, and is pretty non-obvious. And doesn't have anything whatsoever to do with mental ray, as I said above.

So what's up?

Back in the day of 16 bit Windows 3.0, running out of "window handles" (each window on screen has a "handle", like an identifier, used by the operating system to keep track of it) was extremely common, and every Windows user recognized the symptoms... windows wouldn't open, or buttons/texts would be missing from dialogs, or windows opened as only borders, or a strange "placeholder text version" of dialogs popped up.... whatever.

You'd think that a "modern" operating system wouldn't have a limit on the number of windows it could have opened, right? With multipled gigabytes of RAM, this shouldn't be an issue... right?

Well... think again. ;)

First of all the number of possible handles is apparently - still - limited to a 16 bit number (that's 65536 possible handles). But the real limit doesn't lie there, coz that's plenty. The real limit lies in the fact that each "window handle" also implies a memory allocation of a special data structure, that lives in a special memory area called the "desktop heap". And this memory area is small. As a matter of fact, by default, on XP (32 AND 64 bits) ... it's 3 megabytes!!!! Thankfully, on Vista it's larger, so Vista users do not need to do anything (except cry over all the other issues with Vista.... but that's for another blog day...)

Practically, this means that at around a few thousand windows (or other handles), things start failing.

Now, the user interface in Max, Maya and XSI are "windowed" UI's. This means that each control in each dialog is considered a "window" (from the point of view of the operating system). And sub-dialogs, little rollouts, etc. are all subwindows, with controls sub-sub-windows, and buttons can be sub-sub-sub-sub-windows, etc.

Anyone who has seen a compelex Max dialog box or Maya UI, and consider that counting every single little box, control, and thing, you'll find that that's a lot of windows. Maya easily consumes a couple of thousand handles all on it's own. (You can see this by telling your task managers "processes" tab to display the "GDI OBJECTS" column)

(Incidentally, this issue is known by Microsoft, to the extent that they try to write their software "windowless", i.e. when you run, say, Internet Exploder, each little thing on the webpage is not a separate window from the OS's point of view, precicely because of this problem!)

All is lost! The Sky Is Falling! Or?

Not at all.

See, the cool thing is that you can set up the size of the "desktop heap" by fiddling with the registry.

However, there are two things to consider when doing this, one fairly benign, and one less so.

The benign issue is that the "desktop heap" actually comes out of a larger memory area called the "Session View" (don't you just love these names?). And the size of the "Session View" is also limited (to 48Mb by default). Which is again adjustable, but that in turn lives in Kernel address space, which also is limited... to another, larger, value. And so on. You get the idea.

So the point is, you can increase the "desktop heap" size by editing the registry, but you can't just do it willy nilly and put in any old value, because you will get other problems, of running out of "Session View" space.

What I did was to up it from 3Mb to 4Mb, and the problems I had pretty much went away immediately.

The second, less benign issue, is that this is a really hairy registry location, and a horribly convoluted registry key, which actually contains a long string of some 200 characters where you have to change one thing in the middle, and the problem is the fact that doint it wrong can turn your PC into a brick.

Let me repeat that: Doing the registry edit INCORRECTLY CAN TURN YOUR PC INTO A BRICK. A DOORSTOP. A BOAT ANCHOR. MKAY!!??

So proceed with caution!

So what do I do?

Well, first of all, be aware of the above. I will take no responsibility for you turning your machine to scrap metal by a clumsy registry edit. Really. Proceed at your own risk, your own peril, and totally on your own responsibility. If you work at a studio, and the machine is not your own, talk to the TD or machine responsible person, point him to this webpage, and let him do it.

Okay?

Made that clear?

If things blow up, do not come crying to me. I warned you. Ok? Good.

The registry key in question is (and if you don't know how to edit the registry, you probably shouldn't be trying this...):

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\SubSystems\Windows

The default value of this key is something like this


  %SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows
  SharedSection=1024,3072,512 Windows=On SubSystemType=Windows
  ServerDll=basesrv,1 ServerDll=winsrv:UserServerDllInitialization,3
  ServerDll=winsrv:ConServerDllInitialization,2 ProfileControl=Off
  MaxRequestThreads=16

...except it's all in one gargantuan long line, requiring you to scroll horizontally. See that "SharedSection" thing in there? After it it says "1024,3072,512"? Well, the 3072 in the middle, that's the "3 megabytes" we are talking about. 4 megabytes is 4 * 1024, i.e. 4096. So what we want to do is change "3072" to "4096".

Having done that, and rebooted, you should be gold.

More information about the desktop heap can be found here, or using, well, Google.

/Z

Maya: No Alpha channel on mia_material(_x)?

2007-10-12T16:14:00.000+02:00

This must rank as the "most frequently asked question ever". (And consequently, the worst use of Google ever, apparently, since CGTalk alone has more threads on the topic than you can shake a stick at).

The problem: You render stuff in Maya, using mia_material(_x) - or any other "mental ray" shader - but you find that those pixels containing that shader has no alpha. What gives?

The reality is that Maya has a very peculiar notion of Alpha... because the Maya software renderer actually has true three-colored "transparency", so transparency gets passed around separately in the most... odd... ways ;)

Hence, to get the Maya system to "understand" a standard shader that uses alpha, you need to check this here little checkbox:

Then, life should be more fun again!

/Z

Hot Fuzz: Hair Revisited

2007-10-09T15:10:00.000+02:00

In a previous post I briefly mentioned hair. People started to wonder about the details of that, so:

If you render hair w. Raytrace shadows and using the normal raytracer, it works.. but takes a while:

Whereas if one enables the Fast Rasterizer, and use Detail Shadow Maps, it can be both nicer looking and faster:

So the question then is... where do I turn this on?

I admit some things can be hard to find, and sometimes they are renamed in the UI of a particular application... for example, the mental ray detail shadow maps are actually not named "detail shadow maps" in 3DS max, they are named "Transparent Shadows". You find them here:

In Maya, however, they have their proper name and are found here:

However, Maya has "special" shadow settings for Hair and Fur one may need to watch out for.

Turning on the "Fast Rasterizer" is easier since it has it's proper name in most applications. Max:

And Maya:

Hope this helps with the "Fuzzy sidekick" rendering. Note that the Rasterizer is great for motion blur and fuzzy stuff, but can be suboptimal when involving many raytraced effects (glossy reflections, etc.)

/Z

Maya's default shadow settings

2007-10-01T14:14:00.000+02:00

No too long ago I wrote about Maya and shadows.

There is another "issue" related to Maya and shadows; the default shadow trace depth on Maya is 1 (called "Ray Depth Limit" in the lights "Raytrace Shadows" panel). This means that even after one bounce (like a reflection in a mirror, or behind a pane of glass) you suddenly do not have shadows any more! This can hugely impact any quality interior GI render, and you can get all sorts of issues caused by this.

NOTE: A common misconception is that the Maya "Ray Depth Limit" on the ray traced shadows is how many surfaces the shadow rays penetrate. This is not so!.

This image is rendered with the "Ray Depth Limit" of 1:

Notice how the light still gladly penetrates 3 blue glass blocks (6 surfaces in total) and still generates a shadow? Yet when viewed through the single red glass block, the view as seen trough it suddenly is completely shadow-less!

Whereas if we turn up the "Ray Depth Limit" to 3, and the "Shadows" depth to 3 in the mental ray render globals (yes, you must change both!) you get:

Another demonstration of this can be found here

So, in conclusion

Make sure to take a look at Maya's shadow settings, making sure to look at

- shadow trace depth (note this must be set on the light (defaults to 1) as well as in the mental ray render globals (defaults to 2))

- "Low" area light samples (defaults to 2x2) and the "High Sample Limit". However the "High Sample Limit" defaults to 0, which turns OFF the "low area light sampling" mode. This is "good" quality wise (you never actually get the "low area sampling") it precludes a particular mia_material(_x) optimization (it tries to control this from the material, driven by importance, but it cannot do so if it is set to 0). I suggest you turn it up to 4. You can generally keep your "low" sampling at 2x2 when you are using the mia_material, but when using other materials, this may be something to watch out for, since they will strictly adhere to the "depth" setting rather than the relative ray importance, like mia_material(_x) does it.

/Z

Famous mental ray myths...

2007-09-28T09:23:00.000+02:00

There is a lot of misinformation out in the world, misunderstandings that gets repeated and turn into "truths" over time.

I ran into a couple of those at EUE and frankly, I had no idea they were so widespread. So from now on, any time I run into these I'm gonna make a post about it.... here's a collection:

You should always use the mental ray shaders, not the built in max/maya/xsi/whatever...

This myth is both true and false at the same time.

The reality is, there are a ton of "mental ray" shaders, from the very old and very primitive "base" shader library (danger) to very new and very modern "architectural" and "production" shader libraries.

So - yes - if there is a brand new shader that comes directly from mental images that does X, and your embedded application may have some other shader that claims to do X as well, then most likely picking the "mental ray" one is better.

But if there is some ancient shader, from the mists of pre-cambrium, that has a "mental ray" variant, and your application has something that looks as nice, is better integrated, etc.... use that in your application

As an example: The base shader library contains a set of shaders like mib_illum_phong, mib_illum_blinn etc.... never use those! Those are the simplest, most primitive shaders. Avoid!

Much rather than anything "mib_illum_blinn" use the Maya "Blinn" or the 3ds max "Standard" material in "Blinn" mode, or whatever. But even better, use the mental ray mia_material (Arch&Design in max). This is new, mental ray optimized, and we try to integrate it as much as possible into each app.

The old rusty mib_illum_* shaders will have all sorts of issues, interface poorly with the product (no render elements/channel support, no support for diffuse/specular switches on the lights, etc.), handle indirect illumination incorrectly, and so on.

Your apps own integrated materials are mental ray translations of the applications software-renderers material to the "best possible" mental ray counterpart. Your apps own materials are the one most guaranteed to interface with the app's own "features", such as specual switches on light, render channels, whatnot.

And then the mia_material(_x) ("Arch&Design") which we try to make as a "top of the line" thing, and we really try to integrate with as many of the applications own feature as humanly possible.

If it doesn't say "mental ray" dont use it

Similar to above, people have gotten the idea that if a feature doesn't explicitly say "mental ray" or "mr" on it, it is directly unsuitable for use with mental ray.

While this may happen in some odd cases, most of the time, most application features are actually quite well integrated with mental ray.

One of the most scary thing I heard at EUE was someone who asked "You can't use the 3ds max photometric lights with mental ray, right?".

I almost fell off my chair. If you want to render anything even remotely physically correct you should always use the photometric lights. But this guy had been misled by some other lights in the non-photometric category having "mr" in the name.

The reality is that those lights (The "mr Omni" and "mr Spot") are simply lights supporting things that do not exist at all in the other 3ds max lights.

All 3ds max lights are "mental ray lights" when you render with mental ray. Those two simply expose things that only mental ray can do. This does not mean the others "don't work" with mental ray, or that others are "unsuitable" for mental ray.

(Of course, in the case of max lights, what actually is unsupported in mental ray is the 3ds max "trick" to do "area shadows" on any given light, you instead have to make it a real area light. Hence the "extra" light types, although one could argue that perhaps this distinction could have been hidden away from the user in some other way. Alas, water under the bridge....)

So: Please use the photometric lights!

Never use Shadow Maps

This "myth" is the truest of them all. Yes, most of the time you really shouldn't use shadow maps with mental ray (you should use area lights). As a matter of fact I think at least 3ds max ships with shadow maps globally disabled in the mental ray render globals.... this is simply to get around the fact that max lights actually default to shadow maps.

However, there is a couple of cases where you should use shadow maps. And not just any shadow maps - the mental ray detail shadow maps: Hair. Fur.

Yes - any time you want to render hair, that's the time you whip out the rasterizer and detail shadow maps. Not for an architectural interior, but for your fuzzy sidekick in your space drama!

mental ray is slow

Actually mental ray is very fast, if you do things correctly. If you don't do things correctly it - as well as any other renderer - can be very slow.

First of all - suboptimal defaults. If an application ships with a default final gather setting of 500 rays, a way too low spatial oversampling contrast of 0.002 (which makes very little sense), and the default number of motion blur samples set to "19" when "5" is quite enough, of course it will appear slow.

Fixing all those settings can speed it up an order of magnitude.

But yes, I always get this "PRMan displaces faster" stuff. Of course it does.... until you actually trace a ray.

You see, PRMan lives in mindset where raytracing is so slow that you avoid it like the plague. So it uses a completely different method to render things (the REYES engine) which micro-dices things and spits the micro-polygons into subpixels then into pixels. The very nature of this algorithm gives you displacement practically "for free". Coz they work one micro-poly at the time, and never have to keep a single thing in memory.

A raytracer on the other hand (I alost said "a real renderer" *grin*) would out of necessity need to keep all those poly- and micro-polys in memory to have to intersect rays against. So not only do they need to be created, stored in memory, an accelleration structure must be built to speed up the ray intersections. All taking - yes - more time and complexity than dinking away one micropoly at the time and throwing the results over your shoulder when you are done.

The thing is that in PRMan, if you try to shoot a ray, it too has to do all those things. So the minute you actually shoot a single ray in some .sl shader, *grind*, PRMan has to do what mental ray always does.... and the comparasion suddenly isn't so much in favour of PRMan any more.

Since I am of the opinion that there exists no interesting shading that doesn't involve raytracing, I find the fact that "yes, PRMan can be faster with raytracing off" a completely academic opinion of no practical value (but of course, all speed-tests are run like that, naturally.... *sigh*). I am wholly uninterested in oldschool dinky-toys rendering in a fisher-price universe of reflection maps and reflective occlusion (a trick invented solely to "avoid tracing rays". And of course they build their reflective occlusion maps with mental ray... LOL)

Alas, that's all I have time for today.... more later.

/Z

Sitting in the Shade with Maya... mia_material shadow shading.

2007-09-10T15:24:00.001+02:00

Hello guys and gals.

Just a quick heads-up.

It's come to my attention that there is a performance issue with the "segment" shadow mode and the mia_material shadow shader. It's fine for transparent objects (i.e. it does the job it's "supposed to do").

However, for opaque objects, it is actually doing a bunch of unnecessary work, especially in "Segment" shadow mode - which is the default mode in Maya.

The workaround is very simple; don't use the shadow shader for opaque objects.

Normally, you would use the same instance of mia_material in your surface, shadow and photon slots. Well, if your material is opaque, simply don't put it in the shadow slot. This could gain you some performance.

/Z

(In Max this isn't an issue, since first of all, "segment" shadow mode isn't the default, and secondly, the UI frontend actually does the above already, i.e. it doesn't assign the shadow shader at all to opaque objects.)

Speaking at "End User Event", Sept 13-14, Netherlands

2007-08-29T11:49:00.000+02:00

I'll be one of the speakers at the EUE in Utrecht (25 minutes by direct train from Amsterdam Schiphol Airport). I'll be talking about the new shaders and other mental ray 3.6 stuff.

More info, registration instructions and schedule on eue.3dstudio.eu

Also speaking will be Ted Boardman, Rune Spaans, Jamie Gwilliam, and a truckload of more people.

Pop over if you want to see some fun stuff or just have a word or three. I've been known to talk a word... or three. ;)

/Z

EDIT: Fixed links. Silly me.

Doing BIG renders in Maya

2007-08-27T15:22:00.000+02:00

Since I wrote the below post "Doing BIG renders in max 9" I have been drowned in the question "so how about Maya"?

Well, this is most easily done from your command line, i.e. your windows command line.

Basically, if you want to render the scene "lion.mb" to a 5000x3000 pixel image, you can do that in tiles or stripes or whatever, from the command line. For example you can split it into five 1000x3000 pixel renders that you save in "c:\foo" directory, like so:
render -x 5000 -y 3000 -reg 0 999 0 3000 -rd c:\foo -im part1 lion.mb render -x 5000 -y 3000 -reg 1000 1999 0 3000 -rd c:\foo -im part2 lion.mb render -x 5000 -y 3000 -reg 2000 2999 0 3000 -rd c:\foo -im part3 lion.mb render -x 5000 -y 3000 -reg 3000 3999 0 3000 -rd c:\foo -im part4 lion.mb render -x 5000 -y 3000 -reg 4000 4999 0 3000 -rd c:\foo -im part5 lion.mb
Again, remember, if you are doing FG, to avoid seams between the parts, follow the procedure outlined in the original post, i.e. in brief, speaking "Maya language"

Reduce Resolution
Render to finalgather file by setting Rebuild to "On" and specify a filename
Set the finalgather file to "Freeze"
Do the actual renders

Random Dancing Robots - The Post SigGRAPH Post

2007-08-27T10:25:00.000+02:00

Phew!

Never did I know attending SigGRAPH would make me so busy I wouldn't have time to make a post post SigGRAPH! Oh well, now I finally take five minutes to post a post.

First, I like to remind everyone of the mental ray wiki over at mymentalray.com, which is really taking off with the good help of Martin Breidt, especially his "mental ray cookbook" section.

Secondly, SigGRAPH was a blast, although I missed much due to, as always, lots of meetings. One of the funniest events happened when some random straggler (apparently not completely awake) wandered into one of our meetings and grabbed a coffee and sat down.... after some investigation we figured out the guy was in the wrong room.... he staggered out mumbling "at least I got free coffee". He had no pants on, for some reason. ;)

Thirdly, I can finally talk about mental ray 3.6 and the new toys that come with it. As shown in various posted demos, there are some new architectural stuff, like the portal lights, which allows a really quick set up for perfect quality skylight coming in through small windows.... as well as other things.

Also included is my own little "baby", the production shader library. I promise that you'll read a lot more about that in this blog as things get released. A lot.

For now, you'll have to make do with watching random dancing robots.

But hey, random dancing robots never hurt anyone, did they? Thought so.

/Z

SIGGRAPH 2007

2007-08-02T16:11:00.001+02:00

Hello all.

I'm going to SigGRAPH 2007 conference in San Diego.

I made a twitter account which I'll try to keep updated with my "whereabouts" so that anyone wanting to run into me knows approximately where I am. Be warned, I'm pretty filled up schedule-wise, but there are gaps....

There will also be some nifty posts here, methinks... stay tuned.... *grin*

/Z

Nice Water with mia_material (Arch&Design)

2007-06-27T13:15:00.001+02:00

I was asked how to do more "realistic" water using the Arch&Design (mia_material) shader, since the available presets we ship is only for a surface, i.e. it does the reflections, but you can't actually see into the water, like thus:

The intent for the preset is for nice quick ocean surfaces and similar. What it really shows you, is that water really doesn't have much color, it simply reflects the physical mental ray sky...

Anyway, what to do about seeing "into" the water?

The simple fix is to simply turn "transparency" up. If we turn it up to 1.0
and set a transparency color of "watery blue" we get the following result:

While this is nice, it isn't very realistic. Note how there is a very sharp transition from air to "underwater" which looks strange.

The reason for this is that we used a transparency color, and as the manual says, intensity changes "at the surface of a solid" isn't really what reality does.

If we change our transparency color back to white, and instead turn on the refraction "Color at Max Distance" (refr_falloff_on) and set the distance (refr_falloff_distance) to the depth of the pool, then enable the "Color at Max Distance" (refr_falloff_color_on) and set that color (refr_falloff_color) to the same "watery blue", we will get this result:

Now, the color at the bottom of the pool (at the designated depth) is pretty much the same, but it fades towards that color, rather than immediately hitting it at the surface.

This is nice, but now we have the opposite problem; the surface is nigh invisible.

So we can dial in a compromise. First of all, crank up your "Diffuse" to 1.0. Why? Because the energy conservation will only give as much "diffuse" as there is NOT transparency.

We used to have a diffuse of 0.1 in the original water preset. Now we have "replaced" this with transparency (since transparency is 1.0). But the water preset really uses the "diffuse" to simulate a bit of scattering in the water (see how the very top image is a bit greenish, and you can actually see the shadow "on" the water). So to get the same "look" you can set the diffuse to 1.0, and the transparency down to about 0.9 ... that leaves (1.0-0.9)*Diffuse amount of diffuse.... = 0.1 -ish.

This gives a wee bit of surface back (there is a bit of transition, that then goes darker by depth, which is both better than the hard transition in image 2, and the non-existent one in image 3), plus we actually see slightly (but just slightly) how the pool edge casts a shadow on the water.

Now, of course, a pool needs caustics.

Make sure your water surface is set to "generate caustics" both in the instance properties, and that the material is set to "use refractive caustics" (do_refractive_caustics=1) and that caustics is on in the render options.

One "trick" to quickly get nice and "sharp" caustics is to lower the number of interpolated photons. Interpolating more yields a more "smeared" caustics look - picking a lesser number of photons is a quick-and-dirty way to "sharp" caustics, but at a fairly low quality. (The non-dirty solution is to send in mo' photons).

I used only 5 (!) photons in the lookup for this render:

Of course, we are just using a bump map for surface detail, if we add an actually ripple to the surface, it looks a wee bit more realistic:

...and finally, the "round corners" shader is an ideal way to give that little "surface tension fillet" that water does around submerged objects:

I hope this is useful for your next pool render. ;)

/Z

Doing BIG renders in max 9

2007-06-14T20:49:00.000+02:00

I have received several questions on how to make very very high res renders in 3ds max with mental ray.

When you do this, there is a memory issue (worse on 32 bits) which makes some tiles turn black, and you get poor results. mental ray actually renders the image fine, but the individual image tiles get lost due to memory being full when sent over to max.

To help you solve this issue, I wrote this very simple script (Warning: I am not a MaxScript expert, this may cause your computer to catch fire and your wife to move to Iowa, use at your own risk) that allows you to split a render into "tiles".

You simply run the script, and a dialog pops up asking you how many "tiles" you want to break the image into. Pretty simple and self-explanatory. The render is broken into pieces, and saved as separate files, which you then can assemble in, say, Photoshop or similar.

There is one important point, though;

If you are using final gathering in the scene, you must do this from a saved final gather map, or you may get artifacts in the joints between the pieces.

In theory, I could add this to the script, but since I am no MaxScript expert (see above) and since I am not made out of time... I didn't.

To do this yourself:

1. Temporarily reduce the resolution of your render to something that renders withouth memory issues.
2. Turn on FG and tell it to write to file.
3. Set your min/max sampling temporarily to 1/64 and 1/64 for a really fast render (FG quality will not be affected by this!)
4. Render.
5. Set back original sampling (and resolution).
6. Set the FG map to "Read Only"
7. Run the script to do your "split render".

Hope this helps anyone stuck in "cannot lender large resolutions" land.

Enjoy.

/Z

Conversion Script Update

2007-06-11T20:58:00.000+02:00

The conversion script mentioned a few posts down has gotten a wee bit of an update, with some long standing bugs removed. Get the update script here. (Follow installation instructions in this post below).

Enjoy. (Or not, if it doesn't work, again... ;) )

/Z

"Rainbow" effects with the mia_material (Arch&Design)

2007-05-10T18:33:00.000+02:00

I was asked an innocent question about interference- and dispersion like effects in rendering, and I did the following nifty test:

Basically, it's three layered copies of the material. One contains the diffuse component, and the reflection color set to red, and with an anisotropic reflection. The other two has the diffuse component set to black, and have green and blue reflection colors respectively.

The anisotropy is the same but I modified the anisotropy angle slightly between the three. This gives really neat "rainbow effects" like in a CD-Rom surface.

Enjoy the trick.

/Z

Using mia_roundcorners to render eyes....

2007-04-24T13:56:00.000+02:00

On Jeremy Birn's "lighting challenge" the discussion came to the trouble of rendering the little "glint" at the bottom of an eye, where the surface tension causes the tear fluid to form a little arc, which tends to catch the highlight, and is an important cue for us judging the "mental state" of the person we are viewing (since more fluid creates an arc with a larger radius, and hence a more pronounced highlight, and hence a more "teary eyed" look).

I immediately realized one could use the mia_roundcorners shader to acheive this effect:

Note that to get an arc between two different surfaces, the "allow_different_materials" switch must be ON. Also note that to create a "concave" arc, the surfaces must actually intersect, AND have their normals oriented "outwards" correctly (click image for detailed view):

Have fun with this tip ;)

/Z

Understanding Photometric and Radiometric units and their application to computer graphics

2007-03-22T12:39:00.000+01:00

(Note: This post is 1st draft and will be updated and probably gain some figures and images, probably of gnomes.)

Or: "How to understand photo- and radiometry using only gnomes with basketballs"

Photometry. Ah.

The word alone have many people running for the hills. Going to the fine Wikipedia page in the subject isn't likely to clear things up much. Why so many units, why so confusingly similar, yet different, and how many candela is one lux anyway?

Even I - and I worked with this professionally for years - had to have this stuff gnawing on my brain for quite a while until I finally grokked it all.

I think a good 90% of the explanations out there simply lacks the ability to visualize the problem, or they start on a way too high level, mathematically speaking.

So we'll gonna make this really simple, and we're going to use gnomes and basketballs. But first we're gonna talk to per, and kick a candela out of the house.

Talking to our friend "Per"

If you ventured to the wikipedia page you've seen that many of the photo- and radiometric units is expressed in a this-per-that fashion (cd/m^2, lm/sr) ... lets let the meaning of this sink in, and lets take a familiar example to let it sink in.

Many people ask things like "how many candelas go in one lux", when the question has no answer. "But it's all light" people grumble.

Well, yeah, but It's like asking "how many miles goes into 20 miles per hour" - it absolutely makes no sense without additional information.

To fully understand this, we must study what we mean by saying "per" something. And lets take something familiar - speed - i.e. "miles per hour".

Location A and location B is 100 miles apart.

How many miles per hour? Well, we can't know yet. We need more information.

Ted drives the distance in two hours.

How many miles per hour? Well, now we can calculate it, but it'll be an average: 50 miles per hour.

However, Ted may have been at a rest stop for one hour, and drove the other hour at 100 miles per hour, and still make the same result. We don't know yet.

So while in one sense we can see "miles per hour" as an average, we can also, in a sense, see it as a miles as a function of time (hours).

I.e. one way to interpret "miles per hour" is to say that "how many miles had ted travelled at time T"?

The same goes for the photometric units. For example, lumen (lm) is a measure of power, but power going off in all directions. However lumens per steradian (lm/sr) is a measure of how many lumens go in a particular direction (Steradians is a measurement of an angle in 3D space).

Keeping this interpretation of "per" in mind, makes things a lot easier, and makes it easier to understand that just because you know the lumens, you do not necessarily know the lumens-per-steradian. Sure, you can infer an average, just like we did with Ted's speed, but without actual values, we can not say that there is a certain amount of lumen going in some particular direction.

If we do have values, however, conversions are possible, because just like you could measure Ted's speed every second of his journey, and sum up the distance Ted travelled that particular second, the result for the whole journey will be the distance travelled for the whole journey, so does the various lumen-per-steradian (lm/sr) measurement in all directions sum up (or, technically, the term is "integrate") to the total amount of lumens (lm)!

With us so far. Okay. Lets kick out a friend and explain why.

Kicking the Candela

Photometry and Radiometry is very much related. We'll get to exactly why further down, but lets make things simple for now, and say that the lumen (lm) and the Watt (W) are linked. If you know the spectra of the light, you can actually convert one into the other with a simple number, called the luminous efficacy. Whoah. Big word there. The key in that sentence was "know the spectra", though, since the efficacy is different for different spectra. But we'll get to that.

For now, just pretend the lumen and Watt are pretty much interchangeable. A good memory rule for this is that the luMen contains an M and an upside-down M looks like a W.

Now, a unit used a lot in photometry is the candela (cd). A candela is simply a lumen-per-steradian. We'll get to what that means in a second, but if you guessed "light in a particular direction" you are not far off.

The point is that even though cd is well used unit, it is more confusing to understand the units if we use it. It is actually much easier to understand the whole thing if we keep talking about lumens. Then, when it all sunk in, simply learn "cd = lm/sr" and you'll be golden.

A second reason is that on the radiometry side, there is no special unit for the equivalent watts-per-steradian. This makes the radiometry and photometry appear different when they really are not.

No, radiometry and photometry work the same way, it's just about how you weight your measurements. Simplified, Radiometry is about how much radiation (for example light, but not necessarily) there is. Photometry is about how much actual light there is, and how bright it appears to us humans.

So for now we'll just talk about photometry, but with the candela on vacation.

Sounds fair? Okay, lets introduce the gnomes with the basketballs.

How Gnomes Clarify Everything

Instead of talking abstractly about watts, photons, and whatnot, we'll use some much more imaginative imagery, just because it's more fun that way. If you ever find photometry boring, think of gnomes throwing basketballs, and all will clear up.

Imagine a candle flame. But instead of it emitting photons like in the real world, it's made up of a whole bunch of small gnomes, and each of the gnomes has a magic backpack of never ending basketballs. The gnomes grab basketballs out of their magic backpack, and throw them in all directions. Lets say the flame of the candle is about an inch high, so these are really small gnomes, and the basketballs are to scale.

Now if there is a hundred gnomes, each throwing ten basketballs per second in some random direction, this means that from this candle flame, a total of 1000 basketballs per second are thrown. (Also know this is done in zero gravity, so there is no basketball pile on the floor to worry about, basketballs travel in a straight line until hitting something).

So, the amount of basketballs leaving the entire light per second is 1000. To make this easy, lets leave out the "per second" part, and just consider a certain second of time... lets pretend the gnomes are only actually throwing for one second, and then stop, so we can concentrate on the number of basket balls and don't have to say "per second" all the time. It also saves me typing. I'm lazy that way.

Luminous flux (or power)

That which what we just measured is the luminous flux, or luminous power, in lumen. (Little Underground MEN throwin basketballs for one second, perhaps?). It was, to recap, the total amount of basketballs, from the entire light source (the entire candle flame, all 100 gnomes).

Many people are surprised by the fact that the lumen doesn't change by distance, having learned in school that light falls of by a "distance squared" rule.

This can be understood, because to "capture" a lumen (i.e. know how many basketballs in total are thrown) we would, in principle, have to put a bag around the whole contraption, capture the basket balls, and count them. No matter if we put the bag near, or far, the total gathered over this one second will be 1000. (The size of the bag will be different, though.)

But this was a total measurement. The whole light, in all directions. Lumen. Mkay.

Luminous emittance

What about light not leaving the entire candle, but a particular point on the candle? If the lumen measurement was a total for the whole candle, what about the amount of light per unit of area?

This is the luminous emittance, and is measured in lm/m^2 (lumen per square meter). Simplified, you can think about this as a measurement of how much basketballs one particular gnome is throwing, but in all directions at once.

Imagining a contraption to measure luminous emittance is difficult; You would have to rig up some form of sphere of sensors that exists in absolutely every direction, but yet only aim at one tiny point (one gnome). It's also not of such a large practical use.

Luminous intensity

Instead of considering what a particular gnomes i throwing, lets instead turn to which direction the gnomes are throwing the basketballs.

If we only care about the basketballs thrown due north (but by any gnome), we are concerned about the luminous intensity of the candle. I.e. the entire candle emits a certain amount of light in a particular direction.

The unit for this is lumens per steradian (lm/sr). Now since steradians is a measure of angle in space (if you imagine a normal flat 2D angle as a infinite triangle, imagine the steradian as an infinite cone).

Since any basketballs that started out going in a particular direction will continue to do so, any basketballs that were within this given angle when they started, will be within this given angle until they hit something.

So again, surprising to many, the luminous intensity does not change by distance! This can be trivially understood by a laser, which is basically a ruby crystal full of gnomes that are highly trained and throw their basketballs in exactly the same direction. The intensity of the laser ray is the pretty much the same for its entire length (although in reality it gets absorbed, scattered, and is never perfectly parallel to begin with etc, all of which we are ignoring here).

So: Luminous intensity is any basketballs in a given direction, and is measured in lm/sr (lumen per steradian). And yes, this is the "Candela" unit that we are ignoring for now, because when we write it as lm/sr it's much easier to remember that it is really 'light from some object in a given direction')

Luminance

Now remember how we contrasted the flux and the emittance as the former being from the "whole light" and the latter from a point?

The relationship between intensity and luminance is the same.

This is not just how may basketballs are thrown due north by all the gnomes. It's about how many basketballs are thrown due north by one particular gnome, i.e. "per unit surface area".

Since the "all gnomes in one direction" was lm/sr (lumen per steradian) the "one gnome in one direction" obviously is "lm/sr/m^2" (lumen per steradion per square meter).

Since we now understand the notation (and are avoiding the confusing "candela" unit) we understand that this means 'light from some point going in some given direction'. "How many basketballs is gnome 39 throwing due north"?

Amusingly, and still shocking to many people is that this unit too is stubbornly unaffected by distance. If something is a certain number of lm/sr/m^2, it is that at any distance.

But - I hear you yell - my mom told me when I was three that "light from a point source falls off by the square of the distance to the point source". Was mom lying?

No, she wasn't. Except of course that there is no such thing as a point source. Lets talk about

Illuminance

Now it starts to get interesting!

Lets stop for a second to think about those gnomes throwing the basketballs, and considering where these basketballs actually end up.... on some surface.

Illuminance is simply how many basketballs that hit a surface, from any old direction, over some given area. Since "basketballs in any old direction" was lumen, "basketballs in any old direction over some area" is lm/m^2 (lumen per square meter).

"Hey wait", you say, wasn't that "luminous emittance"?

Yes. True. The unit works out to the same, but the meaning is different (light is coming in, not going out). And while the emittance was pretty much useless and hard to measure, the illuminance is extremely useful and easy to measure:

- Draw a square meter
- Wait one second
- Count the basketballs
- Done.

As a matter of fact, this unit is so terribly useful they gave it their own name too. It's called "lux" (lx). But we'll stick with lm/m2 for simplicity, to remember that it's "basketballs in any direction, per unit area".

This is what you generally measure with your run of the mill light meter. Lux meters are readily available and used for a lot of things.

And now, finally, we are starting to get into the distance dependency.

The amount of lm/m^2 (= lux) received from some light depends on the distance to the light together with the lights emission profile.

"Ah" you say, "this is where the distance squared" comes in?

Yes. And... no.

Remember our laser? It most certainly won't follow the distance-squared rule, even when measured as illuminance, because it's light rays are (for all practical purpouses) parallel.

Same goes for light that come from a light that is - for practical purpouses - infinitely far away, which would include the sun.

"But" I hear you yell, "what about this distance squared thing"?

Well.... imagine a point light source. All gnomes, sitting throwing basketballs in exactly the same spot (those 100 gnomes will have it very very crowded). This means that all the basketballs will start at the same point, and fly in straight lines outwards.

Remember that figuring out the lm/m^2 (lux) was easy? Draw a square meter, wait a second, count the balls?

So lets draw a square meter on a wall one meter from our point light. A certain number of basketballs will hit it. Now lets move the light one more meter away. Since the basketballs all diverge from a central point, the basketball density will change as they move away from the light.

A square meter at double the distance will be hit by much less basket balls. As a matter of fact, it will - being 2 times further away . be hit by exactly 4 times fewer basketballs. Yes... distance squared... finally!

But please note this was only exactly true for a light that
- started in an infinitely small point
- emitted light exactly the same amount in every direction

Anything else is more complicated than that but can often be adequately approximated by a "distance squared" rule.

But lights are not infinitely small points, so there must be a different way to look at this?

Yes - there is.

Remember, "illuminance" was the amount of basketballs coming from all possible directions that hit a particular area, i.e. lm/m^2.

So, what if we summed up all the basketballs coming from all possible directions?

This would mean that we would have to look in every particular direction, look at the incoming light from that particular direction, and go over all possible directions and construct the sum (technically, the "integral") of it all.

Okay, so what is 'light from a particular direction' in this context? Is it the luminous intensity or the luminance? Both were "light in a direction"?

Well, we have to keep in mind that we are sitting at some given point, looking around. At every particular direction we look, we see some particular point on some object, which may or may not emit some light.

This means that what we are interested in is the light in a particular direction from a particular point. That was "Luminance", i.e. lm/sr/m^2 (luminous intensity was from the entire light, not just a point on it).

So we look in every possible direction. Most directions will see nothing, and some of those directions will see the candle flame. Now we said that our candle flames luminance was unaffected by distance. However, the distance to the candle flame makes it bigger (closer) or smaller (further). I.e. if it is closer, the candle flame covers more possible directions. The ratio of directions in which we see nothing to directions in which we see candle flame changes. So even though each particular "look" at the candle flame sees the same luminance, disregarding how close and far it would be, the number of "looks" that see it is much larger when closer!

(In tech speak, the closer object subtends a larger solid angle.)

This is what actually causes falloff from a lightsource. And funnily, for most moderate distances, an object twice as far away will show an area (subtend a solid angle) that is four times as small.... so the "distance squared" rule still holds as a good approximation!

Ergo: The illuminance at a point is created by integrating the luminances from all possible directions. For a flat surface, "all possible directions" is bound by a hemisphere above the surface (since the surface itself blocks the other hemisphere).

Now how do you look up "all possible distances" practically? There is an infinite number of them!!

Well, in a rendering context, such as, for example, mental ray's "final gathering", you do not look up an infinite number of directions, but you look up a set number of directions (this is what the finalgather ray count is!).

So final gather rays look around the scene and look for luminance samples, by simply probing the scene.

For direct light, the illuminance is calculated directly based on the lights luminous intensity (number of basketballs from the whole light in a given direction) and the distance-squared rule, because that is easier and more accurate for the renderer to do it that way.

So what about Radiometry, then?

All the photometric units (when expressed using lumen, and ignoring candela) has exact equivalents in radiometry, i.e. we have:

Radiant flux: W
Radiant exitance: W/m^2
Radiant intensity: W/sr
Radiance: W/sr/m^2
Irradiance: W/m^2

The principle is the same, and the basketball analogies work the same. As a matter of fact, the basketball analogy works even better on radiometry, and here's why:

There are different types of balls (wavelengths). There are balls filled with lead, so they are extremely heavy. And there are balls filled with helium, so they weigh nothing at all.

Radiometry is like we are counting the balls.

Photometry is like we are weighing the balls on a scale.

In Radiometry, a ball is a ball is a ball. In Photometry, it may be a heavy ball (green), a light ball (deep red), or a ball of no weight whatsoever (infrared or ultra violet).

... and finally bringing the Candela back

Also, as noted above lm/sr is the same as a candela. Generally, the units lm/sr are written as "cd" and lm/sr/m^2 as "cd/m^2", the latter being a value you probably hear a lot of as luminance measurement of all sorts of things. If you just keep in mind that "cd" means "lm/sr", you know now what that actually means. (Yes, basketballs from a particular point thrown in a given direction)

So what is computer graphics? Radiometry, or Photometry

Amusingly, it is both.

If you take a standard RGB color, you can see each of the R, G and B components as radiometric, but if you calculate the total intensity of the color (which are generally weighted at 21% red, 72% green and 7% blue) is photometric.

I.e. if you consider the white color (1 1 1) to have the intensity "1", then that intensity if photometric. (Had it been radiometric, the intensity of color (1 1 1) would have been considered 3).

Conversely, the actual R, G and B component can be considered radiometric.

Since a pixel value on screen can be considered a measurement of the light from a particular direction coming from a particular point, it means that a pixel value is a luminance (and each of the R, G and B values are radiances).

So the total value of the pixel will have some relation to an actual lm/sr/m^2 (= cd/m^2) value, and the value of each R, G and B component will have some relation to an actual W/sr/m^2 value.

The exact "conversion coefficient" depends on the application.

For 3ds max, the conversion factor between the total pixel value and the luminance in (cd/m^2) is the "physical scale" (found in the exposure control configuration) divided by PI.

Of course, the exposure control itself must be off or it will affect the pixel values. As a trick can be noted, that if you add an exposure control (but keep it disabled!) and set the physical scale to PI (3.1415) and render to a floating point frame buffer, the total pixel values reported when you right click on them (by the "Mono:" heading) are in cd/m^2.

/Z

mental ray Wiki

2007-02-21T08:27:00.000+01:00

The folks over at mymentalray.com has launched a mental ray Wiki.

It's almost completely empty at the moment, but together we could load it up with a lot of mental ray info!

/Z

Max 9: Converting other materials to "Arch & Design"

2007-02-19T20:27:00.000+01:00

If you want to have some cool tools for handling the Arch & Design material in Max 9 (including converting other materials - including vRay materials - into Arch & Design) you can use this script.

Save the file to your 3dsmax/scripts folder, and run it from the "MaxScript" menu.

Then go into the "Customize" menu and choose "Customize User Interface".

Go to "Menus", and on the left side open up the "mental ray" category.

On the right side, open up, say, the "Tools" menu (or any other of your choice).

Drag-and-Drop the "mr Arch Design Tools" to some cool place on that menu.

Voila - you have installed this nifty little add-on.

Note: A much simpler version of this script exists on the max 9 DVD in the sample scripts folder, but this variant is updated.

Enjoy! ;)

/Z

Clouds with mental ray sky

2007-02-17T08:52:00.000+01:00

I keep getting requests from people saying things like "I saw you at SigGraph showing of the mental ray sky and it had clouds in it. How did you do that?".

To which I twirl my moustache and say, 'tis a deep secret....

....just kidding.

Here's the thing. The mia_physicalsky shader uses a 'haze' value to derive a sky color based on the sun position/angle. So a 'hazier' sky is more white/yellowish and a less 'hazy' sky is deeper blue. Okay fine, weather control, you say, but that's not clouds, is it?

Well... actually... it is... if you modulate the haze value across the sky!

Observe this video that I made... it's basically a collection of all test animations done during the development of the sun&sky. Some are bad, some are worse, some are nice, some has bugs in them, some use very low anti aliasing, and none is a peice of art. However they do demonstrate the cloud feature...

What I did was use this texture map (which is a slightly modified version of one I found from some old CD-ROM with public domain sky textures) as a spherical environment map plugged into the haze parameter of mia_physicalsky. That's basically it!

In Maya or XSI you can do this directly, in Max you need to drag&drop your "mr Physical Sky" from your environment dialog into the material editor, uncheck the "Inherit from Sky" and apply the map there.

What is important - though - is this; This is a normal run-of-the-mill LDRI .jpg image, which means it causes a "variation" in the range 0.0-1.0 ... this is way too little for being visible as "clouds" in the sky (the haze has a range of 0 to 15)

So to see results, you need to multiply the level of the texture. How you do this differs between the applications (in Maya you can use the Gain, in Max you use the Output rollout and turn up the RGB Level, etc etc) but setting it somewhere between 5 and 10 tends to look nifty.

Note that this is not a "physically correct" effect in any way, notably because it doesn't actually scatter light, or block light, or create any shadows, or anything like that. But it does simulate "light" cloud coverage very nicely (like high altitude cirrus clouds), and the cool thing is that the clouds coloring automagically follows the sun angle, making very nice sunsets possible....

/Z

Gnomon Workshop Skin Shader Tutorial

2007-02-05T20:24:00.000+01:00

I just saw that the this very cool tutorial about my mental ray skin shader (good old misss_fast_skin), which I enjoyed very much, and I wholeheartedly recommend as a good tutorial on how to use the shaders.

Alex Alvarez has made an over two hours long video tutorial in three parts which can be downloaded from the Gnomon Workshop webpage. It's very informative and teaches many cool tricks.

A couple of details about the tutorial, though, that I thought was worth nothing:

Radii stuff

The tutorial started out by "trial and error" to find the various scattering radii. While this may be "good" as a "understand what does what" thing, I really missed my "rules of thumb" from my written SSS tutorial (available here) about the various values for the scatter radii (i.e. that the subdermal should be "about an inch" and the epidermal "about a third of an inch"). The defaults that are there are actually good if your scene is in millimeters.

Color mapping stuff

Generally, colors are not mapped in the "overall" unless you "know" what you are doing. Yes - as Alex finds out, doing it may make more intuitive sense, and may appear more "predictable" if one expects the "final color" to "look" as the "texture color".

However, the whole intended workflow of the shader is actually not to do that!

Because a lot of the "red tone" of skin should actually come from the subdermal and epidermal layers and actually hardly be present in the color map at all.

I.e. when the shader is "fully" utilized, the color map shouldn't "look" like skin at all; it should look like the skin would look if you peeled it off it's fleshy underpinning (yuck!).

It is true that some highly pigmented areas such as skin "moles" or the lip colors indeed map better in the "overall"... this is because they are a layer "on top" of the rest of the skin and actually "filter" the underlying light (blocking it) and for the lips or for skin moles, mapping "overall_color" indeed makes sense.

I fully understand that this "intended" workflow is very counter-intuitive to the lay person, but skin is such a complex substance with a lot of interaction of light between flesh, blood and the actual epidermal skin layer, it can't be as simple as "map a color map to a Blinn".

Bump stuff

I reall missed any mention about that the "appearance" of the bumps is strongly defined by the "balance" between the "diffuse" and "epidermal" layers... because the bump only applies to the unscattered "diffuse" layer, and the "epidermal" layer looks very similar to the diffuse layer, but slightly scattered and without bumps - hence one of the most important "look development" tools for the skin is to balance these two. I would actually want to see more of that rather than Alex's attempt to "blur" the bumpmap, which I do not think one should do.

Fresnel

Oh, I hate to break it to Alex, but fresnel is pronounced "frenell" [freɪ 'nel] - 'tis the name of a french dude. ;)

Reflections

The fact that Alex used something other than the build in reflectivity I can understand... but I pity the choice of the standard Maya "Blinn". I wholeheartedly suggest to use the mia_material for the reflectivity layer of skin, especially utilizing the "refl_hl_only" flag for superfast "skinny" reflections - more on that in a future post here.

I also strongly suggest to have a high "edge" reflectivity at all times, and generally let the specularity levels "follow" the levels of reflections (after all, "specularity" is really only just reflections of light sources...)

Specularities

The reason the skin shader has 2 layers of specularity isn't really to support different "areas" of skin, it's actually to change the shape of the specular "lobe". The traditional "phong" model with it's "cosine-raised-to-a-power" shaped lobe isn't really very suitable for skin, but by blending a couple of such lobes you can get a combined effect that is.

But all this whiny nit-picking aside, the tutorial is a fantastic piece of work, and I'm impressed with the time Alex took to make it (it's over two hours long!). It's well worth a download for anyone into skin shading in mental ray!

Thanks Alex for making it, and I hope you take my comments in a constructive manner!

/Z

Tricks and Tips for the mia_material (Arch&Design): Volume #1

2007-01-21T15:52:00.000+01:00

Aaah, finally; my latest handywork is finally out on all major platforms!

The material known in 3ds max as "Arch & Design" is actually a shader from the architectural.dll library known internally as the "mia_material". ("mia" is a prefix for "mental images architectural"). It is now available in XSI 6 and Maya 8.5, known as "ArchitecturalMaterial" and "mia_material" respectively.

I had to wait writing tips about this material until now, because the shader hasn't been available to everyone (at least not "officially" ;) ), but now all that is history.

So what is this thing already?

As noted by the documentation, the shader is primarily "intended" for "product design" and "architectural" renderings. By this I mean that it, basically, tries to mimic "reality" of hard surfaced... well... stuff. Nobody is stopping anyone from using it in their next feature film... just because the DLL is called "architectural" doesn't really mean much... it's a general purpose material, no more, no less.

The shader has some cool features, and some "quirks" that can be worth knowing. This post is the first in a series of Tricks&Tips which may be useful when using it.

For example, the feature to disable reflections on the "inside" of objects was intentionally intended as a performance optimization to "quickly" render glass. I'm sort of kicking myself for defaulting that to "on", because:
- it doesn't actually help performance that much
- it causes some side-effects that may be... surprising.

I simply suggest... turn it off. The importance driven ray rejection takes pretty well care of removing truly "unimportant" rays anyway, so the feature is somewhat redundant. Secondly, while it's intent is to remove the "inside" reflections, it actually kills reflection on any flipped face (because, well, the side being hit is.. uh... the "inside"!). So if you have a scene imported from a troublesome CAD system (those LOVE flipping random triangles for no reason whatsoever... it's like it's a secret evil plot... oh no... you're only gonna get 75% of your triangles flipped correctly... ha ha... ) you could suddenly get NO reflections on some of them, which looks really weird... without any "transparency" being involved anywhere! Why? Because the "wrong" triangles are showing their "inside"... and hence.... no reflections... as per the option!

Thousand apologies for this "misfeature" ;)

More to follow, but let me drop a hint; Have you tried combining the SSS shaders with the mia_material's reflection feature?

Also, check out the refl_hl_only flag, and do read the docs there.... it's NOT simply a "highlights only" flag. If you use FG, it's a "super-quick fast fake for the ultra-mega-blurry reflections". Like those of... say... skin.

Stay tuned.

/Z

Stuff you never even knew about mental ray 3.5

2006-12-08T11:17:00.000+01:00

One of the coolest features of mental ray 3.5 is the way the final gathering feature works.

It may deceptively seem to work the same way as before, but it doesn't. One really important point is that each FG point stored isn't just a color, it's a whole set of colors - with directional information (for the tech heads: think spherical harmonics).

What does this mean? It means a lot for bump-mapping!!

In earlier version of mental ray, bumps basically had to be resolved by the adaptivity of the final gathering, causing an extreme density of final gather points due to the variation in the bumps.

But in mr 3.5 it works completely differently; the final gathering is actually calculated on the un-bumped normal vector, and the result is stored including directional data... and then at render time, data is looked up into this directional data.

The result is:

Much lower density of final gather points needed, the existance of bump maps does not increase the density!
Very high quality of directional effects of indirect light on the bump maps, at levels previously impossible.

This makes bumpy surfaces render faster, and resolve in much greater detail, causing details in the bump maps in "dark" areas, i.e. areas only lit by bounce lights or other forms of indirect light such as photons.

The catch:

Some earlier shaders out in the wild intentionally tried to work around this problem. These workaround can potentially interfere with the "correctness" of the new method.

The good stuff:

The cool stuff is that due to this new FG storage format, it is possible to do directional lookups into the FG map. This is how the "Highlights Only" mode in the Arch&Design material works, which can give a very good "visual simulation" of extremely glossy reflections, without actually shooting a ton of rays and taking almost no extra render time!

/Z

RSS Feed added.....

2006-12-07T15:51:00.000+01:00

An RSS feed has been added so you can plug this blog in your RSS catcher thingamabob. Enjoy. Or not. ;)

/Z

Public shader sources has been updated

2006-12-01T15:00:00.000+01:00

The public shader source code available at the mental images FTP site has been updated as of today to the level of the shaders as-shipped with mental ray 3.5 - enjoy.

The public shader sources are available at
ftp://ftp.mental.com/pub/shaders/public-shaders-35.zip

/Z

Who took my "temporal contrast"?

2006-11-29T08:35:00.000+01:00

I've received some questions about the "temporal contrast" option and who stole it from the 3ds max 9 UI.

Here's the deal:

In mental ray 2.1 and earlier, it actually used a temporal contrast, which worked very similar to the overal adaptive sampling contrast. However, this actually yeilds suboptimal motion blur.

So mental ray 3.0 or newer actually takes a fixed number of temporal samples for each spatial sample.

However, the parameter, as exposed in the .mi file format still is "temporal contrast" and is an RGBA color. However, this color isn't actually interpreted neither as a color nor as a contrast at all!

What happens is that a number of temporal samples is calculated from this color as such:

samples = 1.o / min(temporal_contrast)

So this means a "temporal contrast" of 0.2 0.2 0.2 0.2 really only means "5 temporal samples". Nothing else. There is no "contrast" comparisions being done between temporal samples at all!

So... since mental ray does this internally, this was propagated to the max 9 UI as a temporal samples spinner, rather than the old "temporal contrast".

It most likely will be changed in the .mi file format in a future version to a "time samples" instead of "time contrast" keyword.

Hope this is clear as mud... ;)

/Z