Multiple-Scattering microfacet BSDF

[RichardBlank]

Just read this article on cgpress http://cgpress.org/archives/multiple...ith-model.html
Is this possible to implement in the vray shader?

[vlado]

It depends; notice the following: "The performance impact of using multiple scattering within the microsurface is significant and can almost double the render time", depending on the material roughness. The previous version of the paper was maybe a bit better, but required large precalculated tables for each glossiness value, making texture-mapped glossiness somewhat impractical.

Best regards,
Vlado

[joconnell]

Just as a dumb thing vlado, it seems from the paper that the amount of extra light scattering is based on a set of statistics and models rather than being driven by the surface of the object or scene - would it be worth doing something like working out the amount of extra light that's added back to the surface by the process as a curve related to the glossiness and adding that on with a self illumination type cheat that's grounded in reality?

[vlado]

Just as a dumb thing vlado, it seems from the paper that the amount of extra light scattering is based on a set of statistics and models rather than being driven by the surface of the object or scene - would it be worth doing something like working out the amount of extra light that's added back to the surface by the process as a curve related to the glossiness and adding that on with a self illumination type cheat that's grounded in reality?

It's a bit more complicated than that That's kind of what the same author's paper from last year did; however it requires quite a large table for every possible combination of glossiness value, viewing direction and lighting direction, so texture-mapped glossiness becomes a concern (basically, it kind of becomes a measured BRDF).

Best regards,
Vlado

[joconnell]

I getcha - I suppose what I'm thinking can currently be achieved by layering in a slight sss anyway.