Unstructured hexahedral volume meshes are of particular interest for visualization and simulation applications. They allow regular tiling of the three-dimensional space and show good numerical behaviour in finite element computations. Beside such appealing properties, volume meshes take huge amount of space when stored in a raw format. In this paper we present a technique for encoding connectivity and geometry of unstructured hexahedral volume meshes.

For connectivity compression, we extend the idea of coding with degrees as pioneered by Touma and Gotsman [30] to volume meshes. Hexahedral connectivity is coded as a sequence of edge degrees. This naturally exploits the regularity of typical hexahedral meshes. We achieve compression rates of around 1:5 bits per hexahedron (bph) that go down to 0:18 bph for regular meshes. On our test meshes the average connectivity compression ratio is 1:162:7.

For geometry compression, we perform simple parallel-ogramprediction on uniformly quantized vertices within the side of a hexahedron. Tests show an average geometry compression ratio of 1 :3:7 at a quantization level of 16 bits.