Parameterization of Tabulated BRDFs
Ian Mallett, Cem Yuksel · 2016
Measured or simulated data for bidirectional reflectance distribution functions (BRDFs) of various materials is typically stored in a tabulated form by discretizing incoming and outgoing directions over the hemisphere. Since reflected radiance is usually strongly nonuniform over the hemisphere, a uniform discretization of a BRDF usually leads to poor quality at a given memory cost. Unfortunately, there is no universally optimal nonuniform parameterization. In this paper, we provide a mathematical framework for analyzing them with respect to the BRDFs they represent. We use our framework to motivate a parameterization based on Bézier curves: a novel approach that adapts to any given BRDF. Our test results using measured and analytical BRDF models show that it provides superior computational and spatial efficiency for equal quality, as compared to simpler alternatives.