Wavelet-based stratified irradiance caching for efficient indirect illumination

Abstract

This paper presents a new method for efficient computation of indirect lighting in local lighting environments. We establish a separation between the BRDF and the irradiance for each vertex, such that during runtime we are able to quickly reconstruct per vertex irradiance. In reconstructing irradiance, we establish an important relationship between three components: stratified irradiance shared across vertices, the fast wavelet transform, and a wavelet-based nonlinearly approximated inner product. By nonlinearly approximating the BRDF for each vertex, we demonstrate how stratified irradiance has spatial independence in the 2D Haar wavelet domain, in turn allowing for large extents of irradiance samples contributing to many vertices. By expressing irradiance in terms of shared scaling coefficients, we introduce an efficient algorithm for evaluating the inner product between the irradiance and the BRDF. Our system is tailored towards the interactive rendering of static but geometrically complex models which exhibit complex reflectance materials, capable of interactive lighting and interactive view under frame rates of 2-6 fps, ran entirely on a single CPU. © Springer-Verlag Berlin Heidelberg 2007.