thanks for replying so quickly, but what if there are some standins or usd assets at my scene, I can't get those emission shaders. I try to render every light group as a render layer, such as key env fill, and the emission will effect every render layer, I think it will cost some extra render time, only one layer with emission will be enough.I use LPE 'C.*[O]' to add a custom emission aov for every render layer, and remove emission at composite, but I got some weird stuff.
