What I meant is single scattering microfacetted BSDF model which is the main cause of dark glass (& my usual suspect).Dade wrote: ↑Tue Jun 08, 2021 1:58 pmI'm not sure to understand what you mean with "single scatter Specular material": something like mirror (single scatter) Vs. glass (2x scatter, reflect and transmit) ?kintuX wrote: ↑Tue Jun 08, 2021 11:20 amBut I realized what the issue was/is. Basically I was checking BiDir with newly added caustics cahe (SDS paths) on "pool tester scene" where discrapency showed. I found it is caused by single scatter Specular material. And of course BiDir engine shows it brighter since it traces both ways.
Anyway it sounds like a bug in BiDir with some very specific type of path being rendered 2 times, I have to check.
Since I haven't noticed any change in GI brightness with Photon depths of 8, 12, 25 & 64, I imagined Water (Glass surface) is blocking GI contribution to & from pool floor which then only contributes a single bounce using Path engine on the backwall & ceiling in shadow (note I may be totally wrong). Why I made Water shadow transparent and got brighter Indirect Light.