code: function voxelTexture(voxel, side, voxelSideTextureIDs) {
    return voxelSideTextureIDs ? voxelSideTextureIDs.get(voxel&0x7fff, side) : voxel&0x7fff
  }
docs: Vertex format:  x, y, z, ambient occlusion packed_normal, tex_size, tex_id_hi, tex_id_lo  Note: - packed_normal is 6 bits (out of 8) - tex_size is 3 or 4 bits in practice (out of 8) so there are 6 or 7 bits available for future expansion  Voxel format:  * Max 16 bits per voxel * Bit 15 is opacity flag  (set to 1 for voxel to be solid, otherwise rendered transparent) * Texture index is calculated by indexing the voxel ID through voxelSideTextureIDs   This stuff can be changed over time.  -Mik  Retrieves the texture for a voxel