Would it be possible to tell Cycles to not shoot specific rays globally, maybe just for BPT?
It would enable to just shoot necessary rays if you are interested in a specific pass (eg Volume) without having to set up difficult Viewlayers/AOVS. Right now the minimum the user can set is 1 subsample.
Is there a technical reason why the user cannot set it to 0? Would make some things pretty easy to be honest.
I asked Pablo in BlenderHoy if there was a road map in the development of Cycles, and he said yes, he told me this url: https://developer.blender.org/T66305