Investigation on the Torrance-Sparrow specular BRDF model

To describe the directional reflectance characteristics of a specularly reflecting rough surface, Torrance and Sparrow (1967) developed a bidirectional reflectance distribution function (BRDF) model based on geometrical optics. In this study their model is confirmed by a ray-tracing-like simulation, using the same assumptions as in the analytical derivation. The authors also present a simple empirical function that captures the basic features of the analytical model quite well and has been used successfully in BRDF inversion problems including surfaces like roof cover materials and grass canopy.