FXAA 4.0 has as a sharpness slider. FXAA 4.0 applies a special kind of sharping which can be applied in a single pass in conjunction with super-resolution. Here is a bilinear 2x2 up-sample,
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FXAA 4.0 Super-Resolution set to sharp, note the sharpening is different than an un-sharp mask. So extra sharpening with a classic linear filter can be applied over this if desired.
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Sharpening - Without MSAA Input
Sharpening without MSAA input reduces the AA quality slightly. Here is bilinear 2x,
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Here is what this would look like at native resolution,
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And FXAA 4.0 2x super-resolution with sharpening, note in this case the render only renders 25% of the pixels/frame as the image above. The sharpness of this image is limited by FXAA 4.0 only one sample from the current frame and one sample from the prior frame per a 2x2 group of output pixels, and needing to do AA also,
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Another example, here is a native no-AA without resizing,
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And the same with FXAA 4.0 at the sharpest setting,
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