Anti-aliasing

Comparison of no anti-aliasing and 8x MSAA. Click to enlarge

Anti-aliasing is a graphics technique extensively employed in Valve's video games, such as those in the Half-Life series, as well as in other software applications developed by Valve, including Steam and Source Filmmaker, etc. This technique is utilized to enhance the visual quality and reduce the jagged edges, or jaggies, that can appear in computer-generated imagery.

Computer monitors are essentially a large grid of squares that can be set to any color or brightness. As such, it is impossible to draw a perfectly straight line, because no matter how many squares there are, it will never be able to make a perfectly smooth diagonal. This creates a stair-step pattern that is very noticeable the lower the resolution is, which is often referred to in the Video game world as "Aliasing". Spatial anti-aliasing, often referred to simply as Anti-aliasing, is designed to combat the problems of aliasing. In simple terms, Anti aliasing is designed to smooth out that stair-step pattern in images and make them look less pixelated, while not changing the resolution of the final image.

Overview

MSAA

MultiSample Anti-Aliasing (MSAA) was the gaming industry standard of Anti-aliasing, and as such is the only version available in all Source games before Counter-Strike: Global Offensive. Essentially, if a polygon is crossing a multisample point, or subpixel, it detects how many of its neighboring points are also being intersected, then takes the color of that polygon and adds it over the existing image to create a slightly smother line. This creates a smoother line, but does not completely remove the stair-step pattern. This is usually sufficient for most users, however. All Source games contain 4 different settings of MSAA, which include:

2x
4x
6x(only in Source 2004)
8x

What this does is add more subpixels to a specified location and increases the accuracy of the multisampling, at the cost of performance

FXAA

Fast Approximate Anti-Aliasing (FXAA) is a post-processing effect with a low performance cost. The main advantage of this technique over regular anti-aliasing is that it does not require alot of computing power. And also its capable of smoothing out alpha blended textures.(aka Transparent textures). Its main drawback it's that it blurs the final image, so textures will look less sharp. Regular Source doesn't have support for it but as FXAA is a postprocessing effect, it can easily be implemented like with the Source shader editor or with ReShade.

Note:ReShade versions after v5 are not compatible with DX9 based Source games. Use 4.9.1 instead (download mirror here).

TAA

Temporal Anti Aliasing (TAA) is a spatial anti-aliasing technique that combines information from past frames and the current frame to smooth the current frame. TAA, each pixel is sampled once per frame but in each frame the sample is at a different location within the pixel. Pixels sampled in past frames are blended with pixels sampled in the current frame to produce an anti-aliased image. While being cheaper to calculate then MSAA its main drawback is that it can cause ghosting and blurrines to the image(Example here).

The only source engine game that supports TAA is Apex Legends.

CMAA

Conservative Morphological Anti Aliasing (CMAA) is an image based, post processing technique. CMAA uses 4 main steps to reduce aliasing:

Color break detection
Locally dominant edge detection
Simple shape handling
Symmetrical long edge shape handling.

CMAA is only supported in some Source 2 games.

Note:When

Counter-Strike: Global Offensive got ported to

Source 2 (FXAA) support was removed and (CMAA) was implemented in its place.

Media

NO ANTIALIASING

2x MSAA

4x MSAA

8x MSAA

FXAA

Todo: Add a TAA screenshot, also a MSAA 6x

Support

GoldSrc

Game	FXAA	MSAA	TAA
Half-Life Half-Life: Opposing Force Half-Life: Blue Shift Counter-Strike Day of Defeat Ricochet Team Fortress Classic Deathmatch Classic Counter-Strike: Condition Zero Condition Zero Deleted Scenes	NO	YES	NO

Source

Game	FXAA	MSAA	TAA
Source 2004 Source 2006 Source 2007 Source 2009/ Source Multiplayer Source 2013 Half-Life: Source Day of Defeat: Source Half-Life 2 Half-Life 2: Episode One Half-Life 2: Episode Two Alien Swarm Alien Swarm: Reactive Drop Alien Swarm Deferred Source Filmmaker Half-Life Deathmatch: Source Half-Life 2: Deathmatch Half-Life 2: Lost Coast Counter-Strike: Source Team Fortress 2 Portal Left 4 Dead Left 4 Dead 2 Portal 2 Portal 2: Desolation^[confirm]	NO	YES	NO
Black Mesa	YES	NO	NO
Counter-Strike: Global Offensive	YES	YES	NO
Strata Source	YES	YES	NO
Apex Legends Titanfall 2	NO	NO	YES