Unlocked RGB Exponent.

[grantwarwick]

Would be critically useful to unlock seperate RGB values for reflection glossiness, anisotropic value and rotation, and refraction instead of using the RGB Blend material workaround (Seen in the old diamond material trick before dispersion was properly implemented)

Cheers.

Grant.

[Dubbie99]

can't you just use a color?

[grantwarwick]

What do you mean by that? Use a color in these slots?
What if I want the red component to have more blurry reflections than the blue.....I have to make a blend material and blend based on color and its slow as hell....

[Dariusz Makowski (Dadal)]

Mmm interesting idea, is that for metals mainly ? Gold/copper etc etc?

[grantwarwick]

Absolutely, take a look at most real world metals and you will find some level of RGB fringing in the highlights.
It also occurs in other materials commonly as well.

ILM implemented this for iron man 2 although in maya I'm sure they create this shader with a node structure that max isn't currently capable of?

[Dariusz Makowski (Dadal)]

Did they used Vray in iron man? I thought they got their own engine with custom material scans

[joconnell]

Absolutely, take a look at most real world metals and you will find some level of RGB fringing in the highlights.
It also occurs in other materials commonly as well.

ILM implemented this for iron man 2 although in maya I'm sure they create this shader with a node structure that max isn't currently capable of?

Grant - there's a possibility that the fringing is actually coming from metals having a different reflectance curve for each of the red green and blue components rather than it being in the glossiness - I totally get where you're coming from though, that it'd be nice to separate the three and use something like a "highlight spread" approach to replicate a material sample. Metals as a surface though only have on level of polish / glossiness or focus on the surface of the material so it isn't possible for the red part to be less smooth than the blue part for example?

[vlado]

Joconnell is right; reflection strength can be different for red/green/blue, but all wavelengths reflect geometrically in the same way from the same surface so glossiness is the same.

Best regards,
Vlado

[grantwarwick]

Thanks for the clarification Vlado, will you consider the possibility of allowing this separation then so it's possible to reproduce the fringing?

at least for now I know my shaders were more complex than they needed to be!

[vlado]

I will have to think about it; it should be possible quite easily, I think.

Best regards,
Vlado

[grantwarwick]

Thank you Vlado

Did they used Vray in iron man? I thought they got their own engine with custom material scans

No, they didn't, but during their RnD phase they realised they had to decouple the RGB values to reproduce the fringing seen in anisotropic brushed metal.
Yes, they did experiment with acquiring sampled BRDF's but ended up using a modified Cook-Torrence model due to the complexity of the sampled data and trouble reproducing realism in different lighting environments.



"But Snow explains that while a BRDF scanner is quite good for many surfaces it does not scan any anisotropic surface well as the result is so directional: “If you look at the small little round rivets on the suit that had concentric brushed circles, and you get these little bow-tie looking reflections from them”. ILM learnt quite a lot about the anisotopic surfaces were doing and created an anisotropic specular function for the silver suit in particular. “So we added a function that would change the behavior of the highlight depending on the direction of the brushed direction on that part of the suit.”

Snow does not feel that they totally nailed the anisotropic materials. “But that wasn’t the only problem, even though the metals were looking good, and Iron Man holds up really well and one or two of the shots I couldn’t tell later which bits of the suit we’d done – he was inside, then he was flying outside – he was in a range of lighting set ups and even though we set Iron Man up in a standard sand box environment, we were having to retool and tweek his material for each different lighting setup we were having to put him in.”

[joconnell]

I found the exact same thing on a recent film. We set up a vehicle in an idealised environment to look as best as possible but when lined up with the live action asset that it was to be blended with it didn't match at all. The live action asset was rather boring by comparison and so we had to make a load of adjustments and dull everything down. If you make a surface that's technically real that's all very well and good as a starting point, but if it looks dull and uninteresting then you start making adjustments to give it more "life"

[Dariusz Makowski (Dadal)]

Heya

Mah thanks very much for the info ! Quite interesting, I had a debate some time ago with my coworker about doing this to our shaders but he ended up convincing me that the RGB differences are so tiny and small that we would not notice them anyway... can you by any chance show an image of reference that you look at when creating metal like that? Was wondering how far it reach.

Thanks, bye.

[grantwarwick]

(Iron man Mark 2 Live action suit)

[joconnell]

I wonder was that an oxide / patina coating rather than a property of the metal?

P.s. I agree with you - It might go away from some of the vray ethos of not allowing the breaking of physically correct properties but it's still very handy to have in the main ui from an artists perspective.