Approximation of Bidirectional Reflectance Distribution Function with 3-Degree Polynomial

The purpose of this article is approximation of BRDF with functions of argument cos(x). The described approach proposes usage of two functions for BRDF approximation. One of them is a cubic polynomial (with argument cos(x)) and the second one is the function, that assures monotonous falling of the function. Usage of this approach leads to considerable reduce of the approximation error and increases accuracy of the object's highlights representation.