Wavelet encoding of BRDFs for real-time rendering

Abstract

Acquired data often provides the best knowledge of a material's bidirectional reflectance distribution function (BRDF). Its integration into most real-time rendering systems requires both data compression and the implementation of the decompression and filtering stages on contemporary graphics processing units (GPUs). This paper improves the quality of real-time per-pixel lighting on GPUs using a wavelet decomposition of acquired BRDFs. Three-dimensional texture mapping with indexing allows us to efficiently compress the BRDF data by exploiting much of the coherency between hemispherical data. We apply built-in hardware filtering and pixel shader flexibility to perform filtering in the full 4D BRDF domain. Anti-aliasing of specular highlights is performed via a progressive level-of-detail technique built upon the multiresolution of the wavelet encoding. This technique increases rendering performance on distant surfaces while maintaining accurate appearance of close ones.