FXAA is an effective, performance-light form of anti-aliasing developed by NVIDIA's Timothy Lottes, and has been featured in games like Skyrim and Batman: Arkham City. Lottes is currently working on a fourth version of the technology, and has detailed it today on his blog.
(Left image is standard bilinear with 3/2x in width and height, right image is FXAA 4.0 with 3/2x in width and height)
FXAA 4 is described as "a combination of a demosaicing/deinterleaving, super-resolution, and anti-aliasing algorithm all in one tiny full screen pass." Its goals are as follows:
1. Aid in the support of film quality visuals for games.
2. Ultra high quality/cost anti-aliasing.
3. Decouple rendering resolution from display resolution.
FXAA can also be used in older games, such as Duke Nukem 3D, and with surprising results. As you can see below, the image where FXAA 4 is enabled has a considerably smoother image quality, but there is also a slight decrease in the overall sharpness.
(Left Image; no AA, right image; FXAA 4)
The results of FXAA continue to improve and the latest prototype is showing promising results. We are looking forward to seeing FXAA 4 in future games, but for the time being, you can click the source to see more images of it in action.