This patch removes the min bounces settings, instead making Russian roulette
termination use a sqrt() for the termination probability to do path termination
a bit later on average. This also matches typical view transforms a bit, giving
more importance to dark corners.
Some scenes render faster with more noise, others slower with less noise. For
the benchmark scenes it seems to be a good trade-off. Tests with GTX 1080 on
Linux:
| |Before|After|After (equal time)|
|BMW| | | |
| |24.77s|17.41s|24.86s|
|Classroom| | | |
| |17.71s|12.36s|17.68s|
|Fishy Cat| | | |
| |23.98s|20.57s|23.93s|
|Koro| | | |
| |29.98s|26.12s|30.12s|
|Pabellon| | | |
| |20.77s|24.12s|20.78s|
Brightness differences in Fishy Cat are due to indirect sample clamp.