1. A volumetric data organization method for organizing data associated with active voxels in a voxel block, where active voxels are those for which information has been obtained or provided, the methods comprising: causing each active voxel in a column of voxels in the voxel block to be associated with a respective consecutive memory location in a first group of memory locations associated with said column; and causing position information indicating positions of the active voxels in said column to be stored in respective said consecutive memory locations of said first group.