diffuse pass + fresnel

[sharktacos]

I'm expecting the diffuse render pass (render element) to be flat colors. Like it is illustrated here:
http://www.spot3d.com/vray/help/maya...erelements.htm

However when fresnel is checked in the VrayMtl, there is shading on the diffuse render element (from the edges of the fresnel).


Is that correct behavior?

[vlado]

It is correct, yes. The reflections dim the diffuse component.

Best regards,
Vlado

[sharktacos]

It is correct, yes. The reflections dim the diffuse component.

Best regards,
Vlado

I understand that the diffuse would be dimmed there in the final render, but I would expect that to happen in the "raw lighting" element, and that the "diffuse color" element would be flat colors. The darkening from the fresnel would then come from multiplying the two in comp (like it does for the rest of the diffuse light component).

Is there a reason that the fresnel darkening is happening in the "diffuse color" rather than in the "raw light" element?

[vlado]

...but I would expect that to happen in the "raw lighting" element, and that the "diffuse color" element would be flat colors.

Why would you expect that? The Fresnel effect is a material property, not a light property (same as if you use a texture for the reflection color). The raw lighting element is just the total amount of light that reaches the surface; it does not depend in any way on the Fresnel properties of the surface itself.

Best regards,
Vlado

[sharktacos]

Makes perfect sense, thanks for the explanation!