This paper considers an application of the method of representing a complex amplitude as a superposition of plane waves to take birefringence in photolithographic systems into account. The image in transmitted light under partially coherent lighting is conducted according to the source integral method. This paper shows the computational costs of the proposed method, also mentioning the benefits of GPU computation for problem-solving of this type. Special aspects of GPU computation for non-graphical problem-solving are described. This paper introduces estimates of span time in case of computation by means of the mentioned method with GPU as well as CPU. This paper shows the results of simulating the point-spread function under different conditions.