Most of the heavy R&D is over and the result is a new spatial-only algorithm for FXAA 4.0. Note, the only reason this algorithm exists is because it is also the base for the temporal algorithm. The spatial-only algorithm lives somewhere around FXAA 3.11 PC at a medium quality setting, but at the perf a little above FXAA 3.11 Console. Have not profiled yet, so do not actually know.
The aim here is performance for huge resolution rendering or super-sampling. The spatial-only FXAA can also resize just like the temporal version (but lower quality), and it will also support in-line super-sample down-sampling, taking 2 or more FXAA filtered results per output pixel to support ultra high quality in one pass. Super-sample stills will need to wait until another post.
However, !/$ the spatial+temporal solution is the way to go, easily 4x higher quality for nearly same cost.
Spatial-Only Algorithm Enlarge + Sharpen
Similar to the interjection mods, added a built-in classic "halo-ing" sharpen into FXAA 4.0. Below is an example enlarging and sharpening (set at a very subtle 50%) with the spatial-only algorithm. The sharpening can amplify edge noise, EDIT: edge noise and poor quality in the shot below is a result of me using the settings for native resolution instead of the correct settings for enlarging (oops it was 4 am),
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Another example this time with a really fail case for bilinear resize, and sharpness turned up,
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Spatial-Only Algorithm Sharpen Without Resize
With the early exit off and edge detection off, setting sharpening to 100% will maintain detail even when the algorithm filters highly detailed textures,
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Spatial-Only Algorithm Sharpen Over MSAA
The algorithm plays nice over MSAA even when sharpening is set to 100%,
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AA at Different Scales
As a side effect of the algorithm functioning when non-pixel aligned, apparently the algorithm can sometimes anti-alias in blurred content. For instance, the left below is the source shot, where the red arrow marks aliasing caused by bilinear upsample of downsampled DOF. The right is the FXAA 4.0 spatial-only algorithm with the early exit removed and sharpening turned off (note the notches got removed),
