Why Oren-Nayar has only reflection, no transmission? about pbrt-v3 HOT 2 CLOSED

I guess some people only use the roughness parameter when calculating reflections and ignore it for transmission -- thus OrenNayarReflection would be then paired with a LambertianTransmission BxDF?

from pbrt-v3.

Hi Ben,

that's a good observation. There is no reason why you couldn't have a microfacet BTDF with diffusely transmissive facets. Since the scattering function of diffuse facets are not Dirac deltas, you'd have to compute (or approximate) an integral as in the case of the Oren-Nayar model for reflection. There is always a space tradeoff in the book (anything we add somewhere needs to be removed elsewhere) -- but it might make sense to add it as an advanced exercise in PBRTv4.

Best,
Wenzel

from pbrt-v3.