Homomorphic factorization of BRDF-based lighting computation

Several techniques have been developed to approximate Bidirectional Reflectance Distribution Functions (BRDF) with acceptable quality and performance for realtime applications. The recently published Homomorphic Factorization by McCool et al. is a general approximation approach that can be used with various setups and for different quality requirements.In this paper we propose a new technique based on the Homomorphic Factorization. Instead of approximating the BRDF, our technique factorizes the full lighting computation of an isotropic BRDF in a global illumination scenario. With this method materials in complex lighting situations can be simulated with only two textures by using commonly available computation capabilities of current graphics hardware.The new technique can also be considered as a generalized approach to several environment map prefiltering techniques. Existing prefiltering techniques are usually limited to specific BRDFs or require advanced hardware capabilities like 3D texturing. With the factorization only common 2D textures are required.