Fast Polyhedral Cell Sorting for Interactive Rendering of Unstructured Grids

João Comba (Stanford University), James Klosowsky (IBM T.J. Watson), Nelson Max (Lawrence Livermore National Laboratory) , Joseph S. B. Mitchell (University at Stony Brook, Cláudio T. Silva (IBM T.J. Watson) and Peter L. Willians(Lawrence Livermore National Laboratory)

Appears in the Proceedings of the 1999 Eurographics


Direct volume rendering based on projective methods works by projecting, in visibility order, the polyhedral cells of a mesh onto the image plane, and incrementally compositing the cell's color and opacity into the final image. Crucial to this method is the computation of a visibility ordering of the cells. If the mesh is "well-behaved" (acyclic and convex), then the MPVO method of Willians provides a very fast sorting algorithm; however, this method only computes an approximate ordering in general datasets, resulting in visual artifacts when rendered. A recent method of Silva et al. removed the assumption that the mesh is convex, by means of a sweep algorithm used in conjunction with the MPVO method; their algorithm is substantially faster than previous exact methods for general meshes.

In this paper we propose a new technique, which we call BSP-XMPVO, which is based on a fast and simple way of using binary space partitions on the boundary elements of the mesh to augment the ordering produced by MPVO. Our results are shown to be orders of magnitude better than previous exact methods of sorting cells.


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