Ways to improve performance of anisotropic texture filtering

We propose a method of reducing the computational complexity of determining the partial derivatives in the process of calculating the position of the projection of pixel on textured plane for Heckbert method, which reduces the number of operations of addition and multiplication through the use of iterative formulas and, consequently, to improve performance. Also, to improve the performance of texture mapping, the proposed methods for caching intermediate results of computations to determine the coefficients of the equation of the ellipse for anisotropic texture filtering.