Bidirectional texture contrast function

We consider image texture due to the illumination of 3D surface corrugations on globally smooth curved surfaces. The same surface corrugations give rise to different image textures depending on illumination and viewing geometries. We study surfaces that are on the average approximately Lambertian. The surface roughness gives rise to luminance modulations of the global shading pattern. The extreme values of the luminance depend on simple geometrical factors such as whether surface micro facets exist that squarely face the light source or are in shadow. We find that a simple microfacet-based model suffices to describe textures in natural scenes robustly in a semi-quantitative manner. Robust statistical measures of the texture yield the parameters for simple models that allow prediction of the BRDF. Thus texture analysis allows the input parameters for inverse rendering and material recognition to be estimated.