hue varied by light angle of incidence.

[jbuttell]

There's a way to do this using a maya lightinfo node, but it appears to be limited to a single source. Is there any way to vary the hue based on the angle of all incoming light...? I feel like I may be overlooking something obvious.

thanks!

[vlado]

It might be possible to do it based on each individual ray of light separately, but it will require some custom coding...

Best regards,
Vlado

[jbuttell]

thanks Vlado, I figured that might be the case. I'd imagine it wouldn't be too complex/expensive of a shader... but not entirely sure. I'd imagine it would be using existing shading info, coming up with an averaged angle based on the incoming light samples... maybe I'm oversimplifying it.

[vlado]

Does it have to be the average of all light samples (compared to shading each light ray separately)? One is physically plausible (shading each light ray), the other one is not (shading based on average angle).

Best regards,
Vlado

[jbuttell]

ahh - yes I think you're right, it isn't the average angle I'm looking for, but the accumulative color based on the light-ray incidence angle samples.

Just for sake of discussion - I'd imagine using something like a simple luminance evaluation might provide a similar end result, but not entirely. One obvious problem of course being that shadows would undesirably contribute to the hue shift.

thanks again. Maybe I'll have to dig into writing vray shaders afterall... can't imagine it would take long, just all of the C++ periphery stuff is intimidating.

[vlado]

Well, I could get you a simple modification of the blinn BRDF that does that (filters the light through a gradient based on the angle between the surface and the incoming light rays); perhaps you can test it and see if it does what you need.

Best regards,
Vlado

[jbuttell]

That's pretty much it in a nutshell, that'd be great I'm interested in ultimately taking the resulting color and feeding it into the FastSSS2 shader (Sub-surface color, maybe also scatter color) for a custom light rolloff. I don't think there's a way to specify a custom BRDF there, so this probably wouldn't work for me? Ideally yes, that extended functionality to roughly tweak the BRDF like this is what I'm after.