Abstract: The directional transmissions at rough, transparent surfaces create a unique visual effect, which could only be rendered with offline methods such as Monte Carlo ray tracing.A rendering algorithm is proposed to achieve real-time rendering of this phenomenon.By treating the directional transmissions as serial filters, we propose an approximate solution for multiple consecutive directional transmissions;the approximate solution can be used to pre-calculate the transmitted distant lighting through multiple rough interfaces, and to store the results to a set of environment maps;by indexing these pre-calculated environment maps, GPU can render directional transmissions and reflections on rough, transparent surfaces in real time.Experimental results show that the proposed algorithm, which was implemented on a graphical hardware, was able to generate convincing rendering results and interactive frame rates.