What Is Anti-Aliasing?

Curves and lines appear less jagged when you use anti-aliasing tools

Brain pixelated, artwork
PASIEKA / Getty Images

Aliasing in images can be described as stair-stepping lines or jagged edges that are often found in lower-resolution displays. The jagged edges are visible because the monitor or other output device isn't using a high enough resolution to show the smooth line. Anti-aliasing, then, is a technology that attempts to resolve the aliasing found in the image.

You might find the option for anti-aliasing if you look through the settings of a video game. Some options might include 4x, 8x, and 16x, though 128x is possible with advanced hardware configurations. Anti-aliasing is often seen as anti-aliasing or AA and is sometimes called oversampling.

How Does Anti-Aliasing Work?

We see smooth curves and lines in the real world. However, when computers render images for display on a monitor, those curves and lines break down into tiny square elements called pixels. This process results in lines and edges that often appear jagged.

Screenshot of 'Half Life 2' without anti-aliasing
Note this scene from 'Half Life 2' without anti-aliasing. There are jagged lines around the buildings, character, and pier. Michael Archambault 

Anti-aliasing reduces this problem by applying a particular technique to smooth out the edges for a better overall picture. This might work by slightly blurring the edges until they appear to lose that jagged quality. By sampling pixels around the edges, anti-aliasing adjusts the color of the surrounding pixels, blending away the jagged appearance.

Screenshot of 'Half Life 2' with anti-aliasing
Note this scene from 'Half Life 2' with anti-aliasing. The edges are smoother around the buildings, character, and pier. Michael Archambault 

Although the pixel blending removes the sharp edges, the anti-aliasing effect might make the pixels appear slightly fuzzier.

Anti-Aliasing Options

Different anti-aliasing techniques deliver a variety of results depending on the hardware capabilities of your PC:

  • Supersample anti-aliasing: The SSAA process takes high-resolution images and downsamples to the necessary size. This approach results in a much smoother edge, but supersampling requires more hardware resources from a graphics card, such as additional video memory. SSAA isn't used much anymore because of how much power it requires.
  • Multisample anti-aliasing: The MSAA sampling process requires fewer resources by supersampling only parts of the image, particularly polygons. This process is not as resource intensive. However, MSAA doesn't perform well with alpha/transparent textures, and because it doesn't sample the entire scene, image quality may be reduced.
  • Adaptive anti-aliasing: Adaptive anti-aliasing is an extension of MSAA that works better with alpha/transparent textures but it doesn't take up the bandwidth and resources of a graphics card the way supersampling does.
  • Coverage sampling anti-aliasing: Developed by NVIDIA, CSAA produces results similar to higher-quality MSAA with only a slight performance cost over standard MSAA.
  • Enhanced quality anti-aliasing: Developed by AMD for their Radeon graphics cards, EQAA is similar to CSAA and delivers higher-quality anti-aliasing over MSAA with minor impact on performance and no increased video memory requirements.
  • Fast approximate anti-aliasing: FXAA is an improvement on MSAA that is much faster with less hardware performance cost. Plus, it smooths out the edges on the entire image. Images with FXAA anti-aliasing can, however, appear a bit more blurry, which isn't useful if you're looking for sharp graphics.
  • Temporal anti-aliasing: TXAA is a newer anti-aliasing process that produces improved results over FXAA by incorporating several different smoothing techniques, but with a slightly higher performance cost. This method doesn't work on all graphics cards.

How to Adjust Anti-Aliasing

Some games offer an option under the video settings to configure anti-aliasing. Others may only offer a couple options or may even not give you an option to change anti-aliasing at all.

Screenshot of AA settings in 'Half Life 2'
Michael Archambault 

You might also be able to customize anti-aliasing settings through your video card’s control panel. Some device drivers may provide you with other anti-aliasing options as well. You can usually choose to have anti-aliasing settings dictated by the application so that different settings may apply to different games, or you can turn anti-aliasing off completely.

Which Anti-Aliasing Setting Is the Best?

This isn't an easy question to answer. Experiment with game and graphics card settings to see which options you prefer. If you find performance is decreased substantially, such as with degraded frame rates or difficulty loading textures, reduce quality settings or try less resource-intensive anti-aliasing.

Graphics cards are continuing to perform better, and newer monitors have resolutions that eliminate most perceivable aliasing. With these developments, tweaking anti-alias settings is less important than it used to be.