I am currently having some trouble with various renderpasses in my rendering process. I have a model that has a large glass sphere in it with other objects behind it. These objects however do not fill the entire sphere, and I want the rest of the sphere to be transparant in the output (Alpha + PNG). Now, for the Beauty pass, this works perfectly fine. But as soon as I add other passes such as Ambient Occlusion or any of the other render passes, the output files do not have transparency for the glass sphere.
I could of course disable the glass sphere for rendering all the other passes, but the sphere has a high IOR. This results in the passes not being refracted properly and not aligning up with the original render for compositing in Photoshop.
Does anyone have an idea how I could fix this while still keeping my render output file transparant? Or am I forced to render with a background?