Time-varying light motion in single convergence.

As light travels fast in the physical world, it is generally hard to capture the propagation of light with a real camera. However, with the development of photon mapping, it is possible to simulate and visualize such fantastic effect. In this paper, we propose a new algorithm based on progressive photon mapping to render the time-varying light motion. By incorporating our algorithm with participating media, we synthesis the animation of time-varying light beams expanding in space with slow motion. Interesting phenomena can be observed in our experiments through designating either a constant light source or a bullet light that only emits instantaneously. Our algorithm is efficient in the sense that all frames of the animation can be rendered with only one convergence of the progressive photon mapping, showing the advantage of revealing the light propagation process by our algorithm. The experiments demonstrate the effectiveness and efficiency of our approach.