@wadeb@mtothevizzah@iralmeida@aras@demofox if you ever want to add more ML components to the engine and pipelines (like gradients of BRDF flowing to a tiny network or optimizing something else using the BRDF), having real gradients will pay off - just my very biased opinion as I both contributed to Slang.D and work precisely on learning things inside real game-like renderers. :) Also, their approach will not work after a light bounce (suddenly everything contributes to everything).