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Guacamole

How does multisampling work?

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How does MSAA work? How can shading be decoupled from the "coverage? I'm using d3d10device and there's a way to read the color of inidividual samples from an msaa buffer, how can there be 8 colors with the shader executed once?

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The fragment shader is run once for that block of samples for each triangle that at least partially covers the block of samples. Then, the value output from the fragment shader is only written into samples that the triangle covers. You get different values per sample from triangles that don't cover all samples.

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Yes, msaa has a variable cost. It's more expensive with more polygon edges in the scene.

I believe worst case it is potentially the same as ssaa, but in practice it's much cheaper. To hit the worst case you'd have to have a ton of polys where each poly only touches 1 sample. That sounds funky.

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