In lens-less projection the illuminating wavefront must be modified, so that after propagation on a certain distance it would form an image on the screen. Formed images will be displayed with a frame rate minimum of 20fps in the case of an animated movie. Thus, the speed of computing is extremely important. Computing might be performed by the central processing unit (CPU) or the graphics processing unit (GPU). Reaching a compromise between computational complexity (as well as the time of computing) and the quality of an obtained image is needed. This leads to a need for a proper iteration number of an algorithm, its parameters and size of computing matrices.