Combining Global and Local Virtual Lights for Detailed Glossy Illumination
Seoul, December 2010
Supplementary materials contain comparison with Progressive Photon Mapping and Stochastic Progressive Photon Mapping.
Accurately rendering glossy materials in design applications, where previewing and interactivity are important, remains a major challenge. While many fast global illumination solutions have been proposed, all of them work under limiting assumptions on the materials and lighting in the scene. In the presence of many glossy (directionally scattering) materials, fast solutions either fail or degenerate to inefficient, brute-force simulations of the underlying light transport. In particular, many-light algorithms are able to provide fast approximations by clamping elements of the light transport matrix, but they eliminate the high-rank part of the matrix that contributes to accurate gloss appearance. In this paper we introduce a solution that separately solves for the low-rank and high-rank (but sparse) components. For the low-rank component we introduce visibility clustering and approximation. For the high rank component we introduce a local light technique to correct for the missing illumination. Compared to competing techniques we achieve accurate gloss rendering in minutes, making our technique suitable for previewing applications, such as industrial design, ecommerce, and architecture, where material appearance is critical.