nVidia's Quincunx AA was met with mixed emotions when it came out with the GeForce 3. While the anti alaised image was close to that of 4x AA, it was criticized for being much blurrier then super sampling anti alaising. QC Anti Alaising places a sub pixel directly in the middle of the pixel. Points 2 and 4 and points 3 and 5 are blended together to produce the colour in point 1. The problem with this form of anti alaising is since there is a high level of colour error, edges and lines often look very blurry.

Quincunx AA

Accuview AA

To counter this, nVidia introduces Accuview AA. In laymens turns, the sub pixels of each pixel have been moved into each pixel. Thus when the blending occurs on points 2-4 and points 3-5, this way the colour samples are not taken from the edge anymore thus reducing the colour error. The resulting image is much cleaner and sharper.

nVidia example

Unfortunately the performance penalty associated with 4xS (Accuview AA) is very high. When using 4xS AA the performance is lower then 4x AA, thankfully not by much though.

No AA	2x AA
Quincunx AA	4x AA
4xS AA

Above is 4x4 Evolution 2. AS we can see, the difference between no anti alaising and 2x is quite large. QC and 4x AA are very close in terms smoothing out the jaggies although QC seems to be a little blurrier then the rest. 4xS is obviously the sharpest of each AA, just look at the yellow lines.