Matrix Row-Column Sampling for the Many-Light Problem

Milos Hasan, Fabio Pellacini, Kavita Bala

Proceedings of SIGGRAPH 2007 (SIGGRAPH 2007, ACM Transactions on Graphics, Volume 26, Number 3)

Abstract: Rendering complex scenes with indirect illumination, high dynamic range environment lighting, and many direct light sources remains a challenging problem. Prior work has shown that all these effects can be approximated by many point lights. This paper presents a scalable solution to the many-light problem suitable for a GPU implementation. We view the problem as a large matrix of samplelight interactions; the ideal final image is the sum of the matrix columns. We propose an algorithm for approximating this sum by sampling entire rows and columns of the matrix on the GPU using shadow mapping. The key observation is that the inherent structure of the transfer matrix can be revealed by sampling just a small number of rows and columns. Our prototype implementation can compute the light transfer within a few seconds for scenes with indirect and environment illumination, area lights, complex geometry and arbitrary shaders. We believe this approach can be very useful for rapid previewing in applications like cinematic and architectural lighting design.

Acknowledgments: National Science Foundation (NSF), Intel Corporation, NVidia for equipment donations.