In order to generate high quality soft shadows with low time cost, a fast rendering algorithm of percentage closer soft shadows was proposed. Based on the technology of percentage closer soft shadows, a multi-scale shadow map was used to preprocess the shadow map. By removing those pixels that contributed less to queries about shadow map, the cost of preprocessing was reduced. Based on the fast traversal algorithm, an effective sampling mode was used to sample search area thus improved the accuracy of traversal results by utilizing sampling information. And then, a reuse scheme was exploited. In the scheme, only one representative pixel was calculated for a group of similar pixels, and the other pixels in the group reused the calculation result of the representative pixel, which reduced the amount of calculation and thus improved the performance of algorithm. Finally, soft shadows were blurred to get more smooth edges. In addition, to determine appropriate parameters, a series of experiments were conducted. In order to verify the validity and versatility of the algorithm, several randomly generated scenarios were used for test and the comparisons with the mainstream algorithms were conducted. The comparison indexes were the quality of soft shadows and the running time of algorithms. The experimental results showed that the proposed algorithm has higher performance while ensuring the quality of soft shadows. Furthermore, the larger proportion of shadows virtual scenes has, the greater performance improvement the proposed algorithm gains.
