What Is Anti-Aliasing?

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

Brain pixelated, artwork

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You could describe aliasing in images as stair-stepping lines or jagged edges often found in lower-resolution displays. The rough 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.

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.

You might find the option for anti-aliasing if you look through the settings of a video game. Some possibilities might include 4x, 8x, and 16x, though 128x is possible with advanced hardware configurations. People also refer to anti-aliasing as AA or oversampling.

Note this scene from "Half-Life 2" without anti-aliasing. There are jagged lines around the buildings, the character, and the pier.

Anti-aliasing reduces this problem by applying a particular technique to smooth out the edges for a better overall picture, such as 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 rough appearance.

'Half Life 2' with anti-aliasing

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 is not used much anymore because of how much power it requires.
  • Multisample anti-aliasing: MSAA requires fewer resources, 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, it might reduce image quality.
  • 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 of 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 might only provide a couple of options or not give you an option to change anti-aliasing at all.

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?

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 critical than it used to be.