Eurographics Symposium on Rendering (2004) H. W. Jensen, A. Keller (Editors) All-Frequency Relighting of Non-Diffuse Objects using Separable BRDF Approximation Rui Wang, John Tran, and David Luebke Department of Computer Science, University of Virginia Abstract This paper presents a technique, based on pre-computed light transport and separable BRDF approximation, for interactive rendering of non-diffuse objects under all-frequency environment illumination. Existing techniques using spherical harmonics to represent environment maps and transport functions are limited to low-frequency light transport effects. Non-linear wavelet lighting approximation is able to capture all-frequency illumination and shadows for geometry relighting, but interactive rendering is currently limited to diffuse objects. Our work extends the wavelet-based approach to relighting of non-diffuse objects. We factorize the BRDF using separable decomposition and keep only a few low-order approximation terms, each consisting of a 2D light map paired with a 2D view map. We then pre-compute light transport matrices corresponding to each BRDF light map, and compress the data with a non-linear wavelet approximation. We use modern graphics hardware to accelerate pre- computation. At run-time, a sparse light vector is multiplied by the sparse transport matrix at each vertex, and the results are further combined with texture lookups of the view direction into the BRDF view maps to produce view-dependent color. Using our technique, we demonstrate rendering of objects with several non-diffuse BRDFs under all-frequency, dynamic environment lighting at interactive rates. Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Picture/Image Generation; I.3.7 [Computer Graphics]: Color, shading, shadowing, and texture 1. Introduction Interactive rendering of objects with realistic materials, com- plex illumination, and shadows continues to present a great challenge in computer graphics. Conventional image synthe- sis techniques such as Monte Carlo ray tracing [18, 38], pho- ton mapping [17], and radiosity [7] simulate complex global illumination effects, but are too expensive for real-time ren- dering. Surface light fields [40, 6] allow for capturing real- istic appearance and real-time rendering of physical objects; however, they do not allow for dynamic lighting. Our goal is to relight non-diffuse objects at interactive rates under dy- namic, complex illumination and changing view. Recently, Sloan et al. [36] introduced the pre-computed radiance transfer approach for shading models with low- frequency environment maps. They propose a compact rep- resentation of light transport functions using a spherical har- monic (SH) basis. Relighting then reduces to a simple in- ner product of the light vector, also represented in a SH basis, with pre-computed transport vectors at each vertex. View-dependent rendering of glossy surfaces uses a pre- computed transport matrix rather than a vector at each ver- tex. Although the technique is fast and compact, it is limited to low-frequency environment maps due to approximation with low-order (25D) spherical harmonics. Ng et al. [28] render all-frequency lighting and shadow effects at interac- tive frame rates by using a non-linear wavelet approximation of the environment map and transport matrix. However, for geometry relighting with changing view, their approach is limited to diffuse objects. Our work extends Ng et al’s geometry relighting tech- nique to handle non-diffuse objects with complex BRDFs. We use a separable decomposition to approximate the BRDF with a few (K) low-order terms, each consisting of a 2D light map and 2D view map. At each vertex, we pre-compute K transport vectors corresponding to each of the K light maps. We compress the transport vectors using a non-linear c  The Eurographics Association 2004.