This is pretty much what we did in the Commandos games back in '97. As explained in other posts, you can't use some simple depth metric for the entire box and z

This is pretty much what we did in the Commandos games back in '97. As explained in other posts, you can't use some simple depth metric for the entire box and z-sort them because elongated boxes will cause problems. One of the reasons to do this instead of Z-buffering is that Zbuffer will not help with transparency, and most games with these kind of needs will use it, for antialiasing sprite edges if nothing else.