To make SSAO work in forward you have to:
- Remove it from the composition lighting PP graph if forward shading
- Add it to a new graph which is run at the right part of the frame (same spot indirect capsule shadows are run)
- Modify SSAO to blend with indirect capsule shadows / clear the texture if first
- Make sure the version of SSAO which only relies on depth is used (no GBuffer normal available)
Everything so far is straightforward.
Then after all that, it may turn out that SSAO is much too noisy because it relied on temporal AA. Making it high enough quality is an open ended task and probably the most difficult part of the whole thing.
I don’t have a lot of time to spare right now unfortunately, deadlines everywhere.