Surface radiance: empirical data against model predictions

In this paper we report an empirical study of departures from Lambert´s law for rough and shiny surfaces. We use a recently reported method to recover estimates of the surface radiance function for objects illuminated in the viewer direction. We compare the radiance data with a number of phenomenological and physics-based reflectance models. The models studied include those of Oren-Nayar, Wolff and different variants of the Beckmann model. Our experiments show that among these models the best fit to the empirical data is found to be the Wolff model for smooth objects and the modified Beckmann model for rough objects.