The first two dimensions of scrambled, shuffled Sobol and
shuffled PMJ02 are equivalent, so this makes no real difference
for the first two dimensions. But Sobol allows us to naturally
extend to more dimensions.
This in turn allows the following two things (also implemented):
- Use proper 3D samples for combined lens + motion blur sampling.
This notably reduces the noise on out-of-focus objects that
are also motion blurred.
- Use proper 3D samples for combined light selection + light sampling.
Cycles was already doing something clever here with 2D samples, but
this is probably(?) more robust, as per the issue reported in
T101356.
In the future this will also allow for proper sampling of e.g.
volumetric light sources and other things that may need three or four
dimensions.