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There are several different ways of generating well-stratified samples; RenderMan uses lookups in pre-generated tables of progressive multi-jittered (PMJ) sample sequences which are suitable for progressive rendering and are stratified in 1D, 2D, and 3D.  The The 1D sample values are between 0 and 1, the 2D samples are on the unit square, and the 3D samples are in the unit cube.  (Practical tips on how to map to other domains are mentioned below.)

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