Background Data for Validation of the He-Torrance Model

We present an experimental study of the angular distribution of light scattered from several rough metallic surfaces, which cover a range of roughness conditions. A BRDF model based on the Kirchhoff approximation was used to demonstrate the relation between surface-height statistics and the angular distribution of the scattered light. To do this, the angular distributions calculated with the BRDF model were fit to the measurements; the surface-height statistics were computed with a composite roughness model, and were used as inputs to obtain the BRDF predictions. We show that the Kirchhoff approximation can be applied to rough metallic surfaces that have multiple scales of roughness and near-, but not perfect, Gaussian surface-height distributions.