Sheen position in the stack

[Da-Krunch]

Hello there,

I've been doing some look development tests and I wonder if sheen shouldn't be placed all the way on top, over coat.

The reason for this is that sheen most usually represents phisical properties that happen on top of a possible layer of coat: fuzz, fibers, more often than not just dust.

For the same reason, probably coat tint should not affect sheen.

[iliyang]

[Breaking the record for longest time to respond to a ticket]

I see what you're saying. But could it even be that coat and sheen are mutually exclusive? What's a good use case where you need both? (Coated cloth, peach sound awkward.)

[Da-Krunch]

Hello Iliyang,
I forget where we landed in the end, but the case I was thinking of is that sheen is often an approximation of effects like dust and fuzz, which can accumulate on top of hard surfaces, which may well have a coating.
I guess, my thought was going to fine dust on top of car paint.

[iliyang]

(Sorry for the delay, vacation season)

Dust over car paint seems like a reasonable thing to want, but is this a proper use case for sheen? Is dust retro-reflective?

If diffuse reflection is what you need to model dust, then I wonder if 'diffuse over specular' is a common enough use case to warrant direct support by the shader. (Rather than resorting to layering one instance of the shader on top of another.) When trying to balance simplicity and expressiveness, the line has to be drawn somewhere.