A Directional Statistics-based Reflectance Model for Isotropic BRDFs

We introduce a novel parametric BRDF model that can accurately encode a wide variety of realworld isotropic BRDFs with a small number of parameters. The key observation we make is that a BRDF may be viewed as a statistical distribution on a unit hemisphere. We derive a novel directional statistics distribution which we refer to as the hemispherical exponential power distribution and model realworld isotropic BRDFs as mixtures of it. We derive a canonical probabilistic method for estimating the parameters, including the number of components, of this novel directional statistics BRDF (DSBRDF) model. We show that the model captures the full spectrum of real-world isotropic BRDFs with high accuracy but with a small footprint. We also demonstrate the advantages of the novel BRDF model by showing its use for reflection component separation and for exploring the space of isotropic BRDFs.