I'm trying to export some extra image planes/shader buffers for my render. But I can't seem to get them to take the alpha of the texture into account and cut it away, like it does in the composited image.

I've tried exporting the image planes as a Vector4 supplying the alpha as the fourth channel, but that doesn't seem to make any difference. Is this at all possible? I'd like to export some occlusion and stuff without re-rendering the frame.