Optical properties (bidirectional reflection distribution functions) of velvet

A detailed investigation has been made of the unusual characteristics of the angular distribution of surface scattering from velvet in the visual region. We present a novel method in which samples of velvet fabric are wrapped around a right-circular cylinder so that reemitted radiance can be measured by a digital CCD camera. This setup makes it relatively simple to acquire a large set of bidirectional reflection distribution function (BRDF) samples. The study reveals that, apart from the grazing specular lobe and an anisotropic backscattering peak near 50 degrees , the overall BRDF's are rather uniform across the whole angular span of observation. Attempts are made to relate these scattering characteristics to the physical and the geometrical structure of velvet.