How 3D Game Rendering Works: Anti-Aliasing
Playing the blame game Mathematically, aliasing is caused where a continuous 'signal' is transformed into a discrete set of values, via sampling. Rasterizing a straight or curved line induces spatial aliasing -- these geometric shapes effectively consist of an infinite number of points between two locations in space, and representing it using a fixed number of pixels will always result in an approximation of that line, no matter how pixels are used. Since the pixelated version of the line is no longer an actual line, moving it about or putting it next to other shapes creates a myriad of vis...
Source: techspot.com