1. Make an object with either an alpha-value less than 1.0 or textured with an alpha texture. 2. Directly behind that object, place an opaque prim (Alpha 1.0, Some opaque texture) 3. Pan the camera so that the alpha prim is in-front of the opaque prim 4. Notice that, at certain times, the opaque box will draw in-front of the semi-transparent box, regardless of their logical distance in the frame. (Good angles are something like 30-40 degrees, but I've seen it happen when looking dead on) Why this seems to happen? Look at the screen-shot. It appears that semi-transparent prims do not get loaded into the depth buffer at all, leaving other prims to draw in front regardless of whether they belong there or not. The result is that the prim in the background draws in-front of the prim in the foreground, when logically it should be reversed.