RADV: everything becomes mirrorlike with default sampler

[jansol]

With RADV, everything looks perfectly mirror-like by default:

Specifying --sampler=uniform-random seems to work around this this.

[juliusikkala]

I've also encountered issues with the sobol samplers on a multi-GPU setup in certain cases, so there's definitely something wrong with the implementation. Will need to look into it when I figure out a way to reliably replicate it on my hardware.