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RenderMan/RIS – In Arnold and 3Delight, light samples are the single "go to" parameter to effectively control image quality when only direct lighting is needed. In RenderMan/RIS, we had to match light sample samples count with BxDF sample samples count to achieve acceptable quality and satisfactory convergence rates. Using light samples only samples only – or BxDF samples only samples only – produced slowly convergent renders. In RenderMan/RIS results data, "N samples" means N samples for both light and BxDF. We did all the tests with the "advanced (mode 4)" light sampler since other samplers did not provide acceptable results for this test case. The samples used by the renderer are the ones entered in the UI and are not squared as in Arnold. Note that we used the path tracer with one bounce instead of the "direct lighting" algorithm for one of the images because of a crash (quality and speed did not seem to suffer although there were some minor differences in the render).
3Delight – We have only one control for the general quality of the render. In the case of direct lighting, 3Delight "understands" that samples are best used for light sampling and that's what it does. As tests will show, those samples have a linear impact on perceived noise levels.
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