"Ecological optics" is complicated to describe due to aspects such as non-convex shapes, color, surface roughness at a variety of scales, shadows and interreflections. The aim of this project is to develop descriptions of the appearance of materials that include systematical variations of scale. Physical reflectance models need to be derived to clarify the relation of the irradiance being a function of the incident illumination and the material properties. Mathematical and statistical approaches will be used to describe textures (images or mathematical descriptions of images) as a function of viewing angles, illumination angles and scale.