Anti-aliasing

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

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 points ^[Clarify], it detects how many of its neighboring points are being intersected and 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, however, is usually sufficient for most users.

Source games contain 4 different settings of MSAA, which include 2x, 4x, 6x, and 8x. What this does is add more multisampling points to a specified location and increases the accuracy of the multisampling, at the cost of performance