multisampling

Multisampling anti-aliasing (MSAA) is a hardware-assisted technique used in 3D graphics to reduce jagged edges on polygonal geometry. It focuses on smoothing edges by sampling multiple locations within each pixel during rasterization, rather than sampling the entire image at higher resolution.

In MSAA, a pixel is subdivided into several sample points (for example, 2x2 or 4x4 grids). During rasterization, the depth and stencil tests are performed per sample to determine which samples are covered by a primitive. The fragment shader is typically executed per pixel, and the final pixel color is formed by blending the contributions of the covered samples. The color buffer stores one color per pixel, while per-sample coverage informs how much of that color contributes to the final result. This approach smooths edges while avoiding the full cost of rendering at a higher resolution.

MSAA offers a good balance of image quality and performance and is widely supported on modern GPUs, commonly configured as 2x, 4x, or 8x sample counts. It is effective for reducing aliasing along polygon edges but does not address all sources of visual aliasing, such as texture filtering artifacts or shimmering in textures. Transparent surfaces and complex post-processing effects can complicate MSAA, sometimes requiring special handling or additional techniques. In practice, MSAA is often used together with other anti-aliasing methods, or with a later post-processing pass, to achieve broader smoothing. It differs from super-sampling anti-aliasing (SSAA), which renders the whole scene at a higher resolution and downscales, at a greater performance cost.