HP Labs Technical Reports

Irregular Grid Volume Rendering With Composition Networks

Wittenbrink, Craig M.

HPL-97-51R1

Keyword(s): tetrahedral cell; scanline algorithms; direct volume rendering; parallel rendering; parallel compositing

Abstract: Volumetric irregular grids are the next frontier to conquer in interactive 3D graphics. Visualization algorithms for rectilinear 2563 data volumes have been optimized to achieve one frame/second to 15 frames/second depending on the workstation. With equivalent computational resources, irregular grids with millions of cells may take minutes to render for a new viewpoint. The state of the art for graphics rendering, PixelFlow, provides screen and object space parallelism for polygonal rendering. Unfortunately volume rendering of irregular data is at odds with the sort last architecture. I investigate parallel algorithms for direct volume rendering on PixelFlow that generalize to other compositing architectures. Experiments are performed on the Nasa Langley fighter dataset, using the projected tetrahedra approach of Shirley and Tuchman. Tetrahedral sorting is done by the circumscribing sphere approach of Cignoni et al. Key approaches include sort-first, on sort-last world space subdivision by clipping, rearrangeable linear compositing for any view angle, and static load balancing. The new world space subdivision by clipping provides for efficient and correct rendering of unstructured data by using object space clipping planes. Research results include performance estimates on PixelFlow for irregular grid volume rendering. PixelFlow is estimated to achieve 30 frames/second on irregular grids of 300,000 tetrahedra or 10 million tetrahedra per second.

12 Pages

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