Coherent Out-of-Core Point-Based Global Illumination

We describe a new technique for coherent out‐of‐core point‐based global illumination and ambient occlusion. Point‐based global illumination (PBGI) is used in production to render tremendously complex scenes, so in‐core storage of point and octree data structures quickly becomes a problem. However, a simple out‐of‐core extension of a classical top‐down octree building algorithm would be extremely inefficient due to large amount of I/O required. Our method extends previous PBGI algorithms with an out‐of‐core technique that uses minimal I/O and stores data on disk compactly and in coherent chunks for later access during shading. Using properties of a space‐filling Z‐curve, we are able to preprocess the data in two passes: an external ID‐sort and an octree construction pass.