VFB composite: how to add mask to a Amnbiant occlusion render element?

[fraggle]

Hello, I would like to work with VFB composite but I can't find a way to used the cryptomate render element with other render element like the Ambian occlusion. The cryptomate is greyout when trying to add it on top of the ambiant occlusion render element. But if I create a folder then I can add the cryptomatebut then I can't used it as a mask to excluse some area from the AO.
What I'm doing wrong?
Thanks

[fixeighted]

Cryptomatte is use for object selection/masking, rather than to use it to exclude a render effect.
That's if I understand the problem correctly.
Post an example image or file and maybe there's a simper method of achieving what you want to do.

[fraggle]

thanks, please find a screenshoot example where it could easier to removed the balck area of the AO pass instead of rendering again.

[fixeighted]

If it's an error in the mesh, so literally a black area caused by a flipped poly, then all you can really do is to paint it out. Cryptomatte won't really help, other than to make the selection of the box.
Can't you just render a crop of the bad area after it's fixed?

[fraggle]

Sure, I was just trying to find a solution without using another program, but I undesrtand that VFB is limited.

[Vizioen]

If you rendered your AO in a different pass then you can use cryptomatte to mask out where you want the AO and where you don't want it, so should be doable.

[vladimir_krastev]

Hi, thanks for posting. You can add crypto matte as mask in VFB. Please check the gif below. Or maybe there is something else that you want to achieve?