Making Better Metal with mia_material

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:

Gold in the Sun

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:

Gold in the Kitchen

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.



Sylvain Berger said...

Hi Zap, this is a great trick.

Maybe you could have add that using a mip_rayswitch_advanced node to use both physical sky for final gather and a hdri environment texture for all other ray would have been interesting.

connections are simple. Create mip_raysitch_advance, connect the physical_sky into the finalGather attribute of the rayswitch shader, create a spherical lookup node, attach a hdri texture in this envir node...then connect the envir shader into the default attribute of the raysitch node.

connect the rayswitch in the camera environment attribute.

works like charm. Lighting and FG is performed by the physical sky and all the reflection, refraction, etc are using the hdri.

I love the production shaders!

Sylvain Berger

Ino said...

I never thought putting such a big value on IOR, I was always trying with values up to 2-3 hehe.

Does anyone know where you could find an accurate IOR list for those "non refractive" materials lol it sounds so wierd, but looks really great.
thx again btw.

David said...

Hey Zap, can you talk about tuning the shaders along with the mia for performance considerations. Like the environment blur node and the reflection settings on the mia materials (interpolation)? And maybe some other tricks for rayswitch shaders that aren't as obvious?

I love the range of features I can use but sometimes I think I'm making the shader work harder than I need.

Great work on the shaders AND the documentation. I LOVE the usability of the documents.

Master Zap said...

David; ask and Ye Shall Receive, see my newest post on mia_envblur.


dyei nightmare said...

hi, your example looks very cool, but i wonder if you could translate it to the mia material of the maya version

Evann said...

Ya would

Evann said...

ya would really love to see the maya version , as im still a beginner and would really like to try these out in maya. Thanks Zap!

Unknown said...


According to the most excellent book 'Physically Based Rendering', the reason conductors have an IOR is that when light energy hits the dead-on, some of that energy is converted to heat. At glancing angles, it reflects more off the surface, making a similar, though not as strong effect as light passing through/bouncing off due to IOR in dielectrics.

Love the blog!

Jenne 'decapitator' van der Meer said...

There is a list of IOR's at http://vray.info/topics/t0077.asp but none of them go really high.. I cant even set it above 4 with finalrender's arch materials..

Unknown said...

Hey Zap,

Great info here, any way you'd be willing to post this scene. I tried it a few times and still can't get my metal as shiny/polished as yours. I'm assuming it's my lighting. Thanks.... John

Wilbert van den Broek said...

Hey Zap,

Im trying to create a discplacement map on a mia material but I couldn't get it to work. With a blinn or lambert it works just fine, but mia material doesn't seem to have a displacement node.
Thanx for the great tips btw.


Wilbert van den Broek


Hi Zap,
what a cool stuff. I appreciate your effort for the mental ray freeks.
good stuff in your blog. I am very much impressed. I am also a mental ray lover. maya 2008 has mental ray mia_materialx and it can give multi pass output (according to documentation) but when i am trying to do a multipass render with that i am not getting multiple pass output. plz help me.



roy said...

does this goes also for a water shader?
for example, in a waterfall exemple, the vertical side will have very weak relections, and will look a bit wierd and dark compared to the horizontal part.

Deathsoul said...

helloooo i would like to ask if somebody knows how to add car decals and symbols if i m using a mia material in maya 2009
i really will love the help
so much thanks for reading :D

Unknown said...

Hi Master Zap,

I've been following a lot of your tutorials and they are all great and helpful.

I would like to ask help if you can provide a tutorial on how to make a realistic stainless steel material that can be used for flat surfaces? like, range hoods, refrigerators, table tops.

I tried following the example you showed in "Making Better Material with mia_material" but it seems to not work on flat surfaces, just rounded surfaces.

Hope you can help me on this.

Once again, thanks for all the tutorials you create.

All the best,

Unknown said...

I was pointed to this post by one of our TDs and this is slightly in-accurate. Natural materials don't much over IOR 2.5. At least not at the reference wavelength.
This is a valid trick but you have to use a super high IOR only because your shader is using the fresnel formula for dielectric materials, not the general one where the IOR is a complex number taking into account light absorption.

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lucas said...

Thanks Zap, I read all that in your accent as a sign of respect! Loves the tips thanks.

cedrico said...

Hey there, @ kobayashy, i've been trying to do what you said in your post, i'm on maya 2014, i can't seem to make it happen! Would you mind giving some insight ? Or a simple scen withe right connections?

Christian said...

At then end of the day looks very awesome this aluminium scaffold, im sure we will keep improve things like that in the future

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