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I'm trying to implement anti-aliasing into a raytracer with super-sampling.

What exactly is adaptive super sampling? I'm picturing it as just sampling all of the pixels which are on the edge of each object. Is that a correct explanation?

Also, is adaptive super sampling a type of MSAA? To my understanding, MSAA is essentially an anti-alising process that does not sample every pixel more than needed/is adaptive.

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It's a special form of anti-aliasing, where the level of AA is floating. So if you have a very complex scene, the program raises the factor of AA and if it's a flat scene without any spectacular things in it, it lowers it. The problem with all other forms of AA is, AA is always on. And that costs GPU time.

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"Adaptive Supersampling" may refer to a lot of different techniques but generally it means a form of Anti-Aliasing where pixels are shaded1 a variable amount. It detects pixels that contain triangle edges and shades these pixels at a higher rate than not-edge pixels.

It is generally faster than pure Supersampling, as it avoids having to shade "nomal" non-edge pixels multiple times. For scenes with frequent depth discontinuities (thin bars, cables, antennas, grass) large parts of the image may get Supersampled which hurts performance.

Although Adaptive Supersampling is slower than Multisampling, it may provide better quality as it can mitigate specular edge artifacts2 to some degree.

Adaptive Supersampling is not generally implemented in major games because it requires rasterizing the scene with a multisampled rendertarget. Such rendertargets may become a substantial graphics memory bandwidth bottleneck as most major game engines use deferred shading3.


1 "Shading" refers to the process (implemented in a shader) of calculating the color of a pixel, how much light it "reflects" into the camera, taking lights, shadows, complex materials, etc into account and is therefore quite expensive and should be done as few times as possible per frame.
2 Specular Edge Artifacts: https://www.youtube.com/watch?v=VWRfLhOY2AA
3 Deferred Shading: https://learnopengl.com/#!Advanced-Lighting/Deferred-Shading

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