FSAA

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FSAA is an acronym which stands for Full Scene Anti-Aliasing.

Comparing graphic with no FSAA and with 8x FSAA

Comparing graphic with no FSAA and with 8x FSAA (Click to view)

Modern graphics cards usually support some method of FSAA or Full Scene Anti-Aliasing to help avoid aliasing and jaggies on full screen images. The resulting image may seem softer, and should also appear more realistic. One tried and true method of avoiding or removing aliasing artifacts on full screen images is over-sampling.

However, while useful for photo-like images, a simple anti-aliasing approach (such as oversampling and then averaging) may actually worsen the appearance of some types of line art or diagrams (making the image appear fuzzy), especially where most lines are horizontal or vertical. In these cases, a prior grid-fitting step may be useful (see hinting).

In general, over-sampling is a technique of collecting data points at a greater resolution (usually by a power of two) than the final data resolution should be. These data points are then combined (down-sampled) to the desired resolution, often just by a simple average. The combined data points have less visible aliasing artifacts (or moiré patterns).

Full Scene Anti-Aliasing by over-sampling usually means that each full frame is rendered at double (2x) or quadruple (4x) the display resolution, and then down-sampled to match the display resolution. So a 4x FSAA would render four over-sampled pixels for each single pixel of each frame.

More often than not, FSAA is implemented in hardware in such a way that a graphical application is unaware the images are being over-sampled and then down-sampled before being displayed.