Comparing a Clipmap to a Sparse Voxel Octree for Global Illumination

E. Arnebäck. Master thesis, Chalmers University of Technology, supervisor E. Sintorn, advisor J. S. Carlson, 30 June 2017.


Voxel cone tracing is a real-time method that approximates global illumination using a voxel approximation of the original scene. However, a high-resolution voxel approximation, which is necessary for good quality, consumes much memory, and a compact data structure for storing the voxels is necessary. In this thesis, as a primary contribution, we provide a comparison of two such data structures: a Sparse Voxel Octree, and a Clipmap.

We implement these two data structures, and provide detailed descriptions of both with many important implementation details. These descriptions are much more complete than what exists in the current literature, and it is the secondary contribution of this thesis.

In the comparison, we find that the octree performs worse than the clipmap with respect to memory consumption and performance, due to the overhead introduced by the complex octree data structure. However, with respect to visual quality, the octree is the superior choice, since the clipmap does not provide the same voxel resolution everywhere.


This master’s thesis was done at Fraunhofer-Chalmers Centre in Gothenburg. I would like to thank my boss Johan S. Carlson for letting me explore a topic I find immensely interesting. Many thanks goes to my supervisor Erik Sintorn for being a valuable discussion partner, and helping me greatly improve the quality of this report.

Photo credits: Nic McPhee