Point/voxel core

Point/voxel helpers convert dense point rows into sparse voxel coordinates and back. The core module exposes the metadata classes and lower-level builders used by the operation wrappers.

The quantization contract is:

\[v = \left\lfloor \frac{p - o}{s} \right\rfloor,\]

where p is a point coordinate, o is the origin, and s is the voxel size. The resulting sparse coordinate row is (batch, v_x, v_y, v_z).

Voxel feature aggregation supports sum and mean reductions over point rows assigned to the same voxel. Devoxelization uses a fixed-width map with eight voxel rows per point for linear interpolation and one effective row for nearest interpolation.