pytorch3d/docs/notes/cubify.md

Cubify

The cubify operator converts an 3D occupancy grid of shape BxDxHxW, where B is the batch size, into a mesh instantiated as a Meshes data structure of B elements. The operator replaces every occupied voxel (if its occupancy probability is greater than a user defined threshold) with a cuboid of 12 faces and 8 vertices. Shared vertices are merged, and internal faces are removed resulting in a watertight mesh.

The operator provides three alignment modes {topleft, corner, center} which define the span of the mesh vertices with respect to the voxel grid. The alignment modes are described in the figure below for a 2D grid.