In order to render images with as low noise and as fast convergence as possible, it is important to use samples that do not clump and do not leave large parts of the sampling domain empty.  We say such samples are well stratified.  There are several different ways of generating such well-stratified samples; RenderMan uses lookups in pre-generated tables of progressive multi-jittered (PMJ) sample sequences which are suitable for progressive rendering and stratified in 1D, 2D, and 3D.

In order to look up in one of the pre-generated sample tables one needs to specify which table to use and which sample number.  RenderMan provides a convenient abstraction class and API for this, called RixRNG.

Generating samples

Bxdf calls ...

Integrators call ...

Generating new sample domains

NewDomain

Tips for using samples

Mapping from unit square to other domains ...

When to use splitting and when not

Shirley remap.  

More information

For more (very nerdy) details about the properties of PMJ samples please refer to the following paper:

"Progressive multi-jittered sample sequences",

Per Christensen, Andrew Kensler, and Charlie Kilpatrick,

Proceedings of Eurographics Symposium on Rendering 2018.