On-the-Fly rendering of losslessly compressed irregular volume data

Very large irregular-grid data sets are represented as tetrahedral mesh and may incur significant disk I/O access overhead in the rendering process. An effective way to alleviate the disk I/O overhead associated with rendering large tetrahedral mesh is to reduce the I/O bandwidth requirement through compression. Existing tetrahedral mesh compression algorithms focus only on compression efficiency and cannot be readily integrated into the mesh rendering process, and thus demand that a compressed tetrahedral mesh be decompressed before it can be rendered into a 2D image. This paper presents an integrated tetrahedral mesh compression and rendering algorithm calledGatun, which allows compressed tetrahedral meshes to be rendered incrementally as they are being decompressed, thus forming an efficient irregular grid rendering pipeline. Both compression and rendering algorithms in Gatun exploit the same local connectivity information among adjacent tetrahedra, and thus can be tightly integrated into a unified implementation framework. Our tetrahedral compression algorithm is specifically designed to facilitate the integration with irregular grid renderer without any compromise in compression efficiency. A unique performance advantage of Gatunis its ability to reduce the run-time memory footprint requirement by releasing memory allocated to tetrahedra as early as possible. As a result, Gatunis able to decrease rendering time by a factor of 2 for very large tetrahedral mesh whose size exceeds the amount of physical memory. At the same time, the smaller working set and better access locality of Gatunimprove the rendering performance by up to 30%, even when the input tetrahedral mesh is entirely memory-resident. CR Categories: I.3.3 [Computer Graphics]: Picture/Image Generation—Display Algorithms; E.4 [Coding and Information Theory]: Data Compaction and Compression.