Texture at the terminator

We identify a neglected source of information in the 3D texture in images of articulated surfaces. The texture is especially noticeable near the terminator of the body shadow. We provide a very simple model that allows us to describe the 3D texture contrast in detail. Experiments involving the data from the Curet database, laboratory observations, and informal snapshots reveal that the observations follow the theoretical expectations very closely. The 3D texture allows one to draw inferences concerning the nature of the light field (collimated to diffuse) and of parameters of the surface roughness that are the vital input to the simplest BRDF models, namely the range of slopes of surface micro facets, the distribution of heights relative to the fiducial surface, and the width of the surface protrusions. Thus 3D texture is a very useful cue when rerendering or BRDF estimations are to be attempted.