Fast Ray Traversal of Tetrahedral and Hexahedral Meshes for Direct Volume Rendering

The importance of high-performance rendering of unstructured or curvilinear data sets has increased significantly, mainly due to its use in scientific simulations such as computational fluid dynamics and finite element computations. However, the unstructured nature of these data sets lead to rather slow implementations for ray tracing. The approaches discussed in this paper are fast and scalable towards realtime ray tracing applications. We evaluate new algorithms for rendering tetrahedral and hexahedral meshes. In each algorithm, the first cell along a ray is found using common realtime ray tracing techniques. For traversing subsequent cells within the volume, Plucker coordinates as well as ray-bilinear patch intersection tests are used. Since the volume is rendered directly, all algorithms are applicable for isosurface rendering, maximum-intensity projection, and emissionabsorption models.