HD Catch Difference

[Realish]

I can't really say this thing with HD Catch is a bug, but when it is used for a secondary solver it does give a much different result then when the unbiased path tracing is used.

First picture is using high hd catch settings.
Second picture uses path tracing only.

[Ludvik Koutny]

Of course, that's why we call HDcache biased ;)


But you can always increase HDcache accuracy at the cost of render time. To decrease bias, i suggest trying following settings:

Precomp branching: 4
HDCache PT Samples: 512

Direction sensitivity: 3
Position sensitivity: 30
Normal sensitivity: 3

(Rest at default)

[Ondra]

Yeah, this is what the "bias" in "biased GI algorithm" is all about ;)

[Realish]

Rawalanche I think your presets did the trick.  It looks a lot better and the speed in incredible.

[Ludvik Koutny]

Most important is to never render final rendering with precomp step larger than 1. While increasing precomp step value in HDcache settings might make HDcache precomp faster, which is ideal for previews, it also means some spots on the image will be fully path traced, and that doesn't pay of in any longer rendering than quick preview ;)

But yeah, increasing sample density and accuracy can also lead to cleaner results in a long run ;)