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by cosmic_cheese 8 days ago
The thing that’s always bugged me about SSAO is the “jitter” visible when the player character or camera moves, which I would imagine is due to it being calculated in screen space. In some cases it’s so distracting it breaks immersion.

Given that accuracy isn’t the goal anyway I’ve often wondered if it wouldn’t be better in many cases to apply a sort of pre-calculated AO that uses a relatively small atlas of shading textures rendered on flat surfaces as decals (disclaimer: I am not a graphics programmer). It’d apply only to angular surfaces (so for example human faces wouldn’t be included) but I’d say that 80-90% of the benefit of AO lies in things like corners of rooms anyway — it’s really just manmade objects that look bad without AO, organic shapes don’t suffer nearly as badly.
2 comments
StilesCrisis 8 days ago
"Baked ambient occlusion" does exist. It only works well in games where most objects are fixed. If there's a lot of flexibility in where objects are placed, then movable objects will stick out too much (they will lack the AO shading). It sounds like you're proposing using it only on static walls, which seems like it'd be totally viable.
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debugnik 8 days ago
Splinter Cell Conviction did this well, ambient occlusion got baked for pretty much all models, even dynamic. The dynamic occlusion for characters was solved by approximating them as a bunch of ellipsoids.

https://www.gdcvault.com/play/1012326/The-Rendering-Tools-an...

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nananana9 8 days ago
The jitter is because it's usually rendered at 50% resolution - you can render it at full framebuffer size and it doesn't jitter but it's kind of hard to justify.
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cosmic_cheese 8 days ago
That might be part of it, but the effect I’m describing includes the shading changing shape. So for example if a bust on a pillar is sitting in a corner, as the camera pans around the bust, AO behind the bust shifts to “wrap” around the edges of the bust which looks strange because no shadow in the real world acts like that.
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zlsa 8 days ago
This is largely because early screen-space AO techniques weren't able to accurately estimate whether the pillar is freestanding (and shouldn't darken the wall) or if it is against the wall (and should darken the wall.)

Modern real-time ambient occlusion techniques can estimate the depth far more accurately and produce correspondingly more believable results, at the cost of performance.

https://www.researchgate.net/figure/Visual-comparison-of-dif...

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