A data structure includes a plurality of voxel element arrays of memory locations, the arrays being arranged and associated with a set of indices whereby indices of the set identify corresponding memory locations in each array. The data structure further includes a base array for storing an identification of a contiguous group of the memory locations in each array in which voxel elements of a corresponding group of active voxels may be stored. A method of employing the data structure includes associating a column of active voxels in a voxel block, with a group of memory locations in each array, each memoray location being associated with a respective index. Geometric representations and attributes of active voxels in the column are stored in respective memory locations of said group.