I don’t know if it’s a bug or if I’m making a mistake. I’ll try to explain you the problem I’m facing.
I’m rendering a scene with a volume scatter shader applied to a box covering my whole scene to simulate fog. When I check the data passes the fog information is baked over it tinting my AO, Normal, Vector, Cryptomatte and so on.
I tried different values for the alpha threshold like 0.0, 0.5, 1.0 and nothing seems to solve this problem.
It’s kinda annoying and makes things problematic for post-production.
That’s weird, the volumetric information should have it’s own pass, doesn’t it? I can’t remember if this happens in 2.79 too but I’d report a bug, have you tried with a simpler scene?
I tried last night on a simple scene (with the release candidate) and all the passes were alright, except for the Cryptomatte, which has some transparency apparently influenced by the volume pass, even if the material is solid. It must be a bug.