Department of Pattern Recognition

(eng): Directionally dependent anisotropic material appearance phenomenon is widely represented using bidirectional reflectance distribution function (BRDF). This function needs in practice either reconstruction of unknown values interpolating between sparse measured samples, or requires data fidelity preserving compression forming a compact representation from dense measurements. Both properties can be, to a certain extent, preserved by means of analytical BRDF models. Unfortunately, the number of anisotropic BRDF models is limited, and moreover, most of them require either a demanding iterative optimization procedure dependent on proper initialization, or the user setting of parameters. Most of these approaches are challenged by the fitting of complex anisotropic BRDFs. In contrast, we approximate BRDF anisotropic behavior by means of highlight stencils and derive a novel BRDF model that adapts such stencils to each type of anisotropy present in the BRDF independently. Our model allows for the fast direct fitting of parameters without the need of any demanding optimization. Furthermore, it achieves an encouraging, expressive visual quality in comparison to rival solutions that rely on a similar number of parameters. We believe that our method represents a promising approach to the analysis and modeling of complex anisotropic BRDF behavior.