Encoding volumetric grids for streaming isosurface extraction

Abstract

Gridded volumetric data sets representing simulation or tomography output are commonly visualized by displaying a triangulated isosurface for a particular isovalue. When the grid is stored in a standard format, the entire volume must be loaded from disk, even though only a fraction of the grid cells may intersect the isosurface. We propose a compressed ondisk representation for regular volume grids that allows streaming, I/O-efficient, out-of-core isosurface extraction. Unlike previous methods, we provide a guaranteed bound on the ratio between the number of cells loaded and number of cells intersecting the isosurface that applies for any isovalue. As grid cells are decompressed, we immediately extract vertices and triangles of the isosurface. Our output is a coherent streaming mesh, which facilitates subsequent processing, including on-the-fly simplification and compression.