mental ray in Round 6

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

Benjamin Buttons Beautiful Bytes

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

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

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. /Z Jonas "Incredible Hulk"

Gnomon Workshop Skin Shader Tutorial

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