Minecraft wiki entry for Historical_effects, associated text: Mixing coordinates functions as follows: for pots at double even coordinates, internal faces will be absent and the pot will be completely unaffected by ambient occlusion. At an odd-even coordinate, two outside faces will be fully lit, two inner faces will be absent, and the other two inner faces will be offset to the nearest multiple of 4 block. At a double-odd coordinate, two faces will be offset to one of the two closest multiple of 4 blocks, and the other two will be offset to the other.