Depth Merge Issue?

Hey all, someone will know better than I, but I think theres an issue with the depth merge? My understanding based on reading the manual is that the depth merge check box will use the z depth info of the loader and place it in the correct layer order with another loader. So if i have a box behind a sphere in a scene and I render them separately, I should be able to merge them together using depth merge and they automatically layer properly, (or you can use the depth offset in the merge to adjust).

Problem is that it seems to only kinda work. I made a scene with six sphere in a grid pattern, I have a box in between two spheres, and a ground plane. The depth merge works fine with the spheres and the ground plane, or the ground plane with the box, but the box and spheres has a hard time. Attached is a screen grab. The box SHOULD be in front of the back sphere and in back of the front sphere, but you can see its actually doing the opposite.

Box is obscured the opposite way where the bg sphere is on top and the fg sphere is behind

depthMerge1.PNG (980.72 KiB) Viewed 1112 times

Secondly, using the foreground z offset, it seems to be going from the bottom up, as opposed to the front to back. I assume its looking at the z depth pixel values and as it goes further back it reveals the image, or whatever, but I wouldn't expect it to do that. You can see in the screenshot that its cut in half from top to bottom as opposed to a depth thing.

Box is cut in half in a way I wouldnt expect.

depthMerge2.PNG (778.38 KiB) Viewed 1112 times

The renders came from the same scene and therefore the depth info is the same. Am I just using it wrong or is it not really usable?

Hard to tell without seeing your depth passes.

Here they are shuffled into the rgb and merged without depth merge on. also the viewer is normalized otherwise it would be 100% white.

Well there's your problem. The value of the depth map needs to coincide with the distance from the camera or camera plane.