I’m having problems making the z-depth or mist pass, because they don’t take care of z-transp materials. and for my scene is necessary because is plenty of grass and trees with leaves.
I have being reading this thread http://blenderartists.org/forum/showthread.php?t=120889 which is really interesting, but even with the solutions proposed I can’t fix it.
I’m be very glad if you could help me, here you have a simple blend file showing the problem.
I’m finding your file hard to follow… little more explanation? All I see is a cube and a sphere over a spotlight background.
By the sounds of it, you’d need to add / multiply / maybe invert etc a pass of the alpha areas over the top of the actual z-pass. The blur is done in post, so it’s a matter of patching the initial grey scale z-pass image.
In the scene there are 3 grids which have the material with ztransp, if you edit the material and change the alpha value to 1 you’ll see that now mist pass will detect three grids, but obviously, without transparency: that’s the strange thing. mist pass and z-depth don’t detect transparent objects.
I don’t know if you load the interface, if you don’t, you must go to node editor and click in the button re-render this layer, then you should see the image in the backdrop.
