What does anti-aliasing actually do to your PC games?

Anti-aliasing makes jagged game graphics look smoother, but some methods hit your GPU much harder than others.

It used to be a flex to get a gaming machine and turn anti-aliasing to the max. If you could get 4x or 8x MSAA without making your game look like a slideshow, you were doing pretty well. These days, that basic graphics option has morphed into an alphabet soup of FXAA, SMAA, TAA, DLAA and other combinations that sound like someone dropped a bag of Scrabble tiles.

Fortunately, they all tackle a similar issue. Games have to represent curved and diagonal edges on a grid of square pixels, which can result in stair-step patterns called "jaggies." Anti-aliasing smooths those rough edges, but there are several ways to do it.

Some ask your GPU to compute additional samples. Others filter the image after it's been rendered, while newer temporal techniques use information from previous frames. The idea is cleaner edges, but there is usually a compromise, such as lower frame rates, softer details or occasional ghosting.

SSAA (supersampling anti-aliasing) takes the brute-force approach, rendering the image at a higher resolution before downsampling it to the final resolution. It works quite well, but is extremely taxing on your GPU, which can result in lower frame rates and other performance issues.

MSAA (multisample anti-aliasing) is a bit more reasonable. It does not supersample the whole image, but instead focuses more samples around the edges of geometry. The more samples you use, the smoother the edges can look, but the greater the GPU load.

There's a catch, however. MSAA primarily addresses geometry edges, while aliasing from materials, textures and transparent surfaces can remain. Epic's current Unreal Engine documentation supports MSAA only with the forward renderer, not its desktop deferred renderer. That's one reason the common 2x, 4x and 8x MSAA modes are not always available in newer titles.

FXAA (fast approximate anti-aliasing) and SMAA (subpixel morphological anti-aliasing) come at the problem after the frame has been rendered. FXAA detects high-contrast edges and smooths them out. It's quick and relatively low-cost, but may soften image detail. SMAA employs more advanced edge and pattern detection to retain sharpness while keeping the performance cost relatively low.