Shape, Surface Roughness and Human Perception

3D Image texture due to the illumination of rough surfaces provides cues about the light field and the surface geometry on the meso and on the macro scales. We discuss 3D texture models, their application in the computer vision domain, and psychophysical studies. Global, histogram-based cues such as the "texture contrast function" allow for simple robust inferences with regard to the light field and to the surface structure of 3D objects. If one additionally takes the spatial structure of the image texture into account, it is possible to calculate local estimates of surface geometry and the local illumination orientation. The local illumination orientation can be estimated within a few degrees for rendered Gaussian as well as real surfaces, algorithmically and by human observers. Using such local estimates of illumination orientation, we can determine the global structure of the "illuminance flow" for 3D objects. The illuminance flow is a robust indicator of the light field and thus reveals global structure in a scene. It is an important prerequisite for many subsequent inferences from the image such as shape from shading.