VrayDirt Exclude Color for compositing

[bobweb]

Hello,

I am not sure, whether I am using this right, maybe someone can clear things up for me:
I usually use VrayDirt in an ExtraTex Render Element to get an Ambient Occlusion pass. In compositing I multiply this pass or use it as a mask for a color correction effect.
So far everythings is fine, but sometimes I want to exclude certain objects from AO calculation for which I can simply put them in the exclude list. But then they become black in the AO pass which is equivalent to maximum occlusion. Since in compositing only the dark areas are used to affect the image, the excluded objects create maximum effect instead of no effect.
Therefore I would like to have the excluded objects in white instead of black. Can this be set somewhere?

I have already tried to just swap black and white in the map to have white occlusion, but unfortunately for some reason it looks a lot worse (falloff, noise) than before.

Thanks,
Bob

[mrhalaby]

try adding the objects you want to exclude to the VrayDirt map in the "result affect" slot, instead of the "exclude" one

[bobweb]

Thanks for the tip, unfortunately this does not work either, because it still gets occlusion from other objects, it only loses self-occlusion and the occlusion effect it has on other objects. Swapping it I get its effect on other objects but also self-occlusion again. Or is there some setting I overlooked?
What I would like to have would be the same as exclude, only in white, i.e. the selected object becomes plain white but still has effect on other objects. My only rather tedious workaround is for now to render masks and fill them up with white in compositing.

[tashko.zashev]

What about if you swap Dirt map Occluded/Unoccluded colors and invert the result in post.

[bobweb]

Thanks, as I said, I had already tried that and it looked worse. I think I have found the problem now: I have just tried it again with 16bit-Exr and according 16bit linear workflow in After Effects, and then it works as expected. With just 8-bit non-linear settings the inversion is calculated wrong and it looks horrible. Actually it also works ok with 8bit-Jpg, but only with linear comp settings as well. So, it would still be easier, if the exclude color could be set to white, but this should work as well.