Corners Don't Look Like That: Regarding Screenspace Ambient Occlusion

Summary

Corners Don't Look Like That:Regarding Screenspace Ambient Occlusion Sean Barrett 2012-12-13 The real, physical Cornell box. From Modeling the Interaction of Light Between Diffuse Surfaces, by Goral et al 1984 Please, feel free to gather better data yourself and prove me wrong. If you do so I'll link to it! Game developers are in love with screenspace ambient occlusion (SSAO). They're so in love with it that they do all sorts of crazy things. Amateur developers post screenshots where convex corners get brighter near the corner. Professional developers release games with bizarre halos and ugly artifacts (look at the floor behind the railing). Even when they avoid those flaws, games with SSAO often still look wrong. And an easy thing to pull out from it: corners of rooms look weirdly dark. I believe this is because people think the corners of rooms actually are dark, and they've allowed this belief to let them write code that produces unrealistic results. More specifically, I attribute the failure of SSAO in these cases to some combination of four factors: Approximation errors due to using SSAO rather than AO Approximation errors due to using AO rather than radiosity Errors in applying the SSAO darkening to all lighting, not just ambient lighting Tuning errors, where the heuristic weighting of the AO effect is too strong I am not an active graphics researcher, so I'm not going to set up a framework and show where these things went wrong. That's the job of people publishing SSAO papers and shipping SSAO in games. For the same reason, the following discussion is not the most scientific nor at all thorough. Perhaps collecting more data would suggest I am wrong. But my personal visual experience doesn't match what people are rendering with SSAO, so I wanted to share that experience; to which end I collected some data. Corners Don't Look Like That (most of the time) In the following, everything is a photograph, not a rendering. Photographs were taken using a Canon 5D Mk II...