Representing geometry data as voxels allows for a massive amount of detail that can be rendered in real-time. Storing this type of data as a directed acyclic graph (DAG) has recently led to immense improvements in memory consumption, which is one of the main limitations often associated with voxel-based approaches. We present a method for further decreasing the memory consumption of voxel data in a DAG through a form of lossy compression, meaning that the data is slightly altered from its original state. Our method clusters similar nodes in the graph together in a way that minimizes the geometric error that is introduced. The amount of compression that is applied can be influenced through a set of parameters that affect which nodes are included in the clustering process and the granularity of the clusters that are detected. The memory consumption of the sparse voxel DAG is reduced from 10% to up to 50%, depending on the characteristics of the scene, while introducing errors that are only visible when viewing the scene from up close.
Our method is complementary to other state of the art compression methods for this data structure, and has a negligible effect on real-time rendering performance.