Topological Triangle Sorting for Predefined Camera Paths

Abstract

We present a preprocessing pipeline for triangle meshes that topologically sorts all triangles for a given camera and scene animation in front-to-back or back-to-front order. This allows us to efficiently render a given animation without depth buffer, and to include transparency. We also remove non-contributing triangles, thus improving render time, especially when applying anti-aliasing. To this end we first record the visible triangles of a sequence of frames. For every frame we create a directed graph storing occlusion information. After a topological sort of this graph, all triangles are sorted properly. The contribution of this paper is the reduction of redundancy by merging the graphs of all frames. The result of our pipeline is a single sorted index buffer, over which we slide a window that yields sorted index buffers for each single frame. Circular dependencies are broken by placing duplicates of the affected triangles in the index buffer. Our sliding window then displays only frame specific triangles in their proper order. We conclude by demonstrating the benefits of removing invisible triangles and disabling the hardware visibility test.