Qualities of optically mixed real materials and photographs--towards a material probe

Natural materials cover a wide range of surface scattering properties, which can be described by the bidirectional reflectance distribution function (BRDF). The lobes of the BRDF may be described by their primary scattering direction (resulting in salient features of the appearance modes at different locations) and generic BRDFs typically consist of several of such lobes. Thus, similarly to describing BRDFs as linear superpositions of scattering lobes, we can describe the appearance of objects consisting of any materials as linear superpositions of objects of different canonical materials. We approach this problem via optically mixing of objects that represent canonical reflectance modes, allowing systematical and gradual variations of materials to test perceptual qualities of generic materials.