Page MenuHome

Multiscatter GGX converges to different result (Path vs Branched Path)
Closed, ResolvedPublic


Debian, amd64

Broken: current master

Multiscatter GGX converges to a different result in Pathtracing vs branched Pathtracing.
It seems that MIS and "Sample all Lights" don't influence the final outcome but it is only related to Multiscatter GGX.
Here are the results, both rendered with 100000 samples.

Steps to reproduce:
Here is a .blend file:

Make one render with "Path Tracing" and one render with "Branched Path Tracing", then compare both.

Thank you!



Event Timeline

Sergey Sharybin (sergey) lowered the priority of this task from Needs Triage by Developer to Confirmed, Medium.

The issue still persists here with build 0f793ee. @Brecht Van Lommel (brecht) did you render my example .blend file before closing this issue?

Tested on Linux now and it does still converge to a different result, maybe something compiler specific. With this many samples to resolve noise I wouldn't be surprised if float precision issues have an effect.

I'm not sure if it is float precision issue, but one can see pretty quickly (after 4000 or 8000 samples) that it will converge to a different result.

I'm happy to say that with current builds (b0823962e9b) this issue is solved. Both methods converge now. The final picture is a bit different from both pictures I originally posted:

I don't know which commit solved this issue, but thank you very much!

Thanks for testing, my best guess is rBd454a44e9, but doesn't really matter.