Moments in Graphics
A blog by Christoph Peters
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BRDF Importance Sampling for Linear Lights

Christoph Peters.
2021–07 in Computer Graphics Forum (Proc. HPG) 40, 8.
Official version

Abstract

We introduce an efficient method to sample linear lights, i.e. infinitesimally thin cylinders, proportional to projected solid angle. Our method uses inverse function sampling with a specialized iterative procedure that converges to high accuracy in only two iterations. It also allows us to sample proportional to a linearly transformed cosine. By combining both sampling techniques through suitable multiple importance sampling heuristics and by using good stratification, we achieve unbiased diffuse and specular real-time shading with low variance outside penumbrae at two samples per pixel. Additionally, we provide a fast method for solid angle sampling.

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Notes

This work has been presented at HPG 2021 on July 7th 2021. The author's version has been published on June 18th.