antialiasing

Antialiasing is a class of techniques used in digital imaging to reduce visual artifacts known as aliasing, especially jagged edges on diagonal or curved lines in rasterized images. Aliasing occurs when a continuous image is sampled by a grid of discrete pixels. The goal of antialiasing is to produce a smoother appearance by reducing jagged edges and by preserving detail while avoiding excessive blurring.

Common approaches include several trade-offs between quality and performance. Supersampling anti-aliasing (SSAA) renders the scene at a higher resolution and then downsamples, producing very high-quality results but with substantial computational cost. Multisample anti-aliasing (MSAA) samples multiple locations within each pixel to determine edge coverage and blends colors accordingly, offering a good balance of quality and efficiency. Temporal anti-aliasing (TAA) uses information from multiple frames to reduce shimmering in motion, though it can introduce mild blurring or ghosting. Post-process anti-aliasing methods such as FXAA, MLAA, and SMAA operate on a finished image by detecting edges and applying edge-aware filtering, delivering favorable performance with variable quality. In font rendering, subpixel rendering (for example, ClearType) leverages the individual red, green, and blue subpixels of LCDs to increase perceived horizontal resolution.

Trade-offs include computational cost, memory bandwidth, and potential blur or ghosting. Real-time graphics often favor MSAA or TAA, while offline rendering can employ SSAA for maximum quality. Antialiasing interacts with transparency, texture filtering, and motion; different methods handle these interactions with varying effectiveness. Applications span video games, graphical user interfaces, and high-resolution text rendering, with suitability depending on scene complexity, display characteristics, and performance targets.