Real-Time Bidirectional Path Tracing via Rasterizationupplemental Material

Computing indirect illumination is still too slow to render a high quality image in only one frame. Additionally, in interactive applications such as video games, response is often more important than image quality. In order to increase frames per second and maintain image quality, we exploit temporal coherence in supersampling (See for example [Knecht 2009; Herzog et al. 2010]). In our system we use several indirect illumination caches corresponding to each subpixel, and only one of them is rendered per frame in a round-robin fashion. To improve indirect illumination quality, we evaluate a differing sample subset for neighboring frames similar to spatial interleaved sampling. To compute the final image of the current frame, subpixels are reused from the cache of past frames. This recycling is done by reverse reprojection caching [Nehab et al. 2007]. If the subpixel is detected in the cache, the cached indirect illumination is reused. The reconstructed indirect illumination L of the pixel s is given as: