Gradient-Domain Path Tracing with Gain Control Strategy

Uniform sampling on the pixel plane makes the rendering quality of gradient domain path tracing differ greatly in different frequency regions. Aiming at this problem, gradient-domain path tracing with gain control strategy is proposed. The average gradient is introduced to calculate the average gradient value of partial areas, to filter and to mark the high-frequency areas and low-frequency ones, then to enhance the sampling of the high-frequency areas by samples in the low-frequency ones. With the continuous update of the high and low-frequency areas at the end of each round of rendering, the samples are allocated adaptively, so as to realize the gain control of the pixel plane sampling. On the one hand, the experiment compares the improved algorithm and the gradi-ent-domain path tracing algorithm under different materials and lighting scenes, the results show that the im-proved algorithm makes the rendering of the high-frequency areas sensitive to the human eye more delicate; on the other hand, the experiment introduces the mean square error, peak signal to noise ratio and structural similar-ity to evaluate the rendered image, and compare the trends of the above three indicators during the sampling process, the results show that the improved algorithm can accelerate the convergence speed of rendering and im-prove the rendering efficiency under the condition of ensuring the same number of samples.