btw
This new
importance option has some small speed issues (not correct balance). G. research now "problem".
It should be at least 50% faster. Also after VCM will be again faster....and after optimization again faster.
The scene is very interesting: deep recurse everywhere. Photon path has so big journey from light source that only a few hits camera.
In Arnold you can see missing transparency photons (almost black shadow behind glass). And for clean render you have to wait around 20-30 min.
Maybe you setup wrong render?
...and you can not compare modern PM engine with anything, is just impossible. Arnold (and others unbiased systems) must calculate billions of paths when Kray3 needs only a couple of thousand.
...still believe in interpolation.... 