Space-Time Hierarchical Occlusion Culling for Micropolygon Rendering with Motion Blur

Abstract

Occlusion culling using a traditional hierarchical depth buffer, or z-pyramid, is less effective when rendering with motion blur. We present a new data structure, the tz-pyramid, that extends the traditional z-pyramid to represent scene depth values in time. This temporal information improves culling efficacy when rendering with motion blur. The tz-pyramid allows occlusion culling to adapt to the amount of scene motion, providing a balance of high efficacy with large motion and low cost in terms of depth comparisons when motion is small. Compared to a traditional z-pyramid, using the tz-pyramid for occlusion culling reduces the number of micropolygons shaded by up to 3.5x. In addition to better culling, the tz-pyramid reduces the number of depth comparisons by up to 1.4x.