I know that in Cycles Z pass is not anti-alisased while Mist pass is normalized anti-aliased. I need the real depth of each pixel (like the Z pass) but with anti-aliased. I don't know if getting that from the Z-pass (by making it anti-aliased) or from the Mist pass (making it not normalized) would be feasible and easier?
The real problem is when looking at the output Z pass, the pixels around thin objects like branches, grass stocks, are kinda sparse and missing. I doubt that could be because anti-aliasing is not on. I wouldn't want to post-process that with filtering, since they may create artifacts. So I am trying to get better anti-aliased depth image.