Topology :

• Use a single-indirection brickmap structure.
• Top-level grid: 256³ bricks (8-bit addressing).
• Each brick contains 32³ voxels (5-bit addressing).
• Total addressable space: 8192³ voxels.

Each brick stores an occupancy counter that is updated atomically: if a voxel changes from 0 to nonzero the counter is incremented, and if it goes to 0 it is decremented.

Why :

Allow fast construction of a sparse data structure to run Kernels in. Avoid construction of an IndexGrid that takes around 30ms for 20M active voxels.