Digging through mplot3d (again), I have come to realize that a lot of its code in art3d.py could be simplified if we had a way to tell collection objects in what order to draw their elements. My proposal is fairly straight-forward. All collections would have an internal _zdraworder attribute that can be anything that can index a numpy array: slice(), array of indices, whatever. The draw() methods will then iterate over their elements returned by indexing with _zdraworder. This will help keep the bookkeeping to a minimum, because everything should be sliced/indexed the same way: offsets, verts, facecolors, etc. The default value will be slice(None), so nothing will change for regular collections. With this, mplot3d can greatly simplify its logic and semantics by focusing on projecting and setting the _zdraworder by running np.argsort() on the projected depth of the elements. Another advantage is that methods like get_facecolors() and set_facecolors() can round-trip in mplot3d (right now, get_facecolors() has to return a z-sorted version of the colors for drawing). For now, I imagine keeping this a private attribute, but I could see some really fancy tricks in the future such as using boolean indexing to mark some elements as visible/invisible, and doing some neat tricks for animations. Thoughts? Ben Root