Parameter Optimization in Sparse Voxel DAGs for Efficient Geometry Representation of Voxelized 3D Scenes

Abstract

This paper addresses the issue of geometry representation of voxelized three- dimensional scenes, using domain-specific hierarchical data structures, utilizing lossless compression. It discusses the details of the sparse voxel directed acyclic graph hierarchical data structure with implemented child node pointers, including a detailed analysis of its construction. Then, based on this analysis, we discuss the possibilities of adjusting its parameters, in order to optimize it in terms of its binary representation size. In particular, the possibility of using various numbers of child node pointer types and the binary representation lengths of these is considered; this is also related to the different binary representation lengths of the child node mask and the different binary representation lengths and meanings of the constituent header tags. The various settings of the data structure parameters are then tested on three models whose original representation – surface polygonal models – was transformed: each model was voxelized to six different resolutions. The results obtained were also compared with an uncompressed representation of the geometry of the voxelized three-dimensional scene, encoded using a regular three- dimensional grid of one-bit scalar values (1b/vox). Based on these tests, using a 16b child node mask, three different child node pointer lengths (8b, 16b and 32b) and an 8b address word length came out as the best parameter combination of the investigated data structure in terms of data representation compactness. In the tests, a 1.88–3.06-fold data compression rate was achieved with this parameter configuration for the used test models and scene resolutions, compared to the traditional SVDAG structure using 32b pointers. The maximum data compression ratio (1098.3) – compared to the 3D grid of 1b/vox scalar values – was achieved with this parameter setting for a scene resolution of 4096 3 voxels.