I am currently participating at the lighting challenge #13 at cgtalk.
I want to use the AO pass in the compositor to add AO to my final image. The AO pass was rendered once and since the scene and camera angle is fixed, there is no more need to do this pass all over again.
And here comes my problem. I tried several approaches of mixing the AO-pass back in, but with no satisfying result.
So I went back to a basic scene with only a cube in it and tried again. First I tried to directly mix the non-ao image with the ao-pass with all obvious operation modes from the mix node, but to no avail.
Then I tried to mix the non-ao image with a fixed color (black, gray) and use the AO-pass as factor to the mixing node. Again, not the result as I get with the the internal renderer.
When I started to tweak the AO-pass with the RGB-Curves tool, I soon realized thtat this is leading nowhere. So I wondered what algorithm is actually used in the internal render. If it is some sort of compositing, then I should be able to get the same result.
Is there anybody here, who could give me some insight into this topic ?
Any help is highly appreciated.