(eng): Visual scene recognition is predominantly based on visual textures representing an object's material properties. However, the single material texture varies in scale and illumination angles due to mapping an object's shape. We present an anisotropy criterion of bidirectional reflectance distribution function (BRDF), which allows deciding if a simpler isotropic BRDF model can be used or if it is necessary to use a more complex anisotropic BRDF model. The criterion simultaneously shows dominant angular orientations for the anisotropic materials. The anisotropic criterion is tested on several isotropic and anisotropic surface materials, with BRDF computed from the measured seven-dimensional Bidirectional Texture Function.