A Hierarchical Volumetric Shadow Algorithm for Single Scattering
Author(s)Baran, Ilya; Chen, Jiawen; Ragan-Kelley, Jonathan Millar; Durand, Fredo; Lehtinen, Jaakko
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Volumetric effects such as beams of light through participating media are an important component in the appearance of the natural world. Many such effects can be faithfully modeled by a single scattering medium. In the presence of shadows, rendering these effects can be prohibitively expensive: current algorithms are based on ray marching, i.e., integrating the illumination scattered towards the camera along each view ray, modulated by visibility to the light source at each sample. Visibility must be determined for each sample using shadow rays or shadow-map lookups. We observe that in a suitably chosen coordinate system, the visibility function has a regular structure that we can exploit for significant acceleration compared to brute force sampling. We propose an efficient algorithm based on partial sum trees for computing the scattering integrals in a single-scattering homogeneous medium. On a CPU, we achieve speedups of 17--120x over ray marching.
DepartmentMassachusetts Institute of Technology. Computer Science and Artificial Intelligence Laboratory; Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
ACM Transactions on Graphics
Association for Computing Machinery (ACM)
Ilya Baran, Jiawen Chen, Jonathan Ragan-Kelley, Frédo Durand, and Jaakko Lehtinen. 2010. A hierarchical volumetric shadow algorithm for single scattering. ACM Transactions on Graphics 29, 6, Article 178 (December 2010), 10 pages.
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