Cycles Development Updates

[DeepBlender]

Caustis is nicely handled by bidirectional path tracers, but Cycles is unidirectional. The reason for this is:

Bidir Pathtracing for cycles?

No, GPU is definitely not the issue. The main problem, as Ace already said, is that Cycles allows you to do things that just don’t work with BiDir - such as e.g. ray visibility or changing your shader depending on the incoming direction. In general, for BiDir to work, everything has to be fully symmetric, tracing the same path from the other direction has to produce the same path - but if you have e.g. the path A<->B<->C, where A is diffuse, C is glossy and B is only visible to diffuse rays, tr…