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Multisample anti-aliasing (MSAA) is a type of anti-aliasing, a technique used in computer graphics to improve image quality.



The term generally refers to a special case of supersampling. Initial implementations of full-scene anti-aliasing (FSAA) worked conceptually by simply rendering a scene at a higher resolution, and then downsampling to a lower-resolution output. Most modern GPUs are capable of this form of antialiasing, but it greatly taxes resources such as texture bandwidth and fillrate. (If a game is highly TCL-bound or CPU-bound, supersampling can be used without much performance hit.)

According to the OpenGL GL_ARB_multisample[1] specification, "multisampling" refers to a specific optimization of supersampling. The specification dictates that the renderer evaluate the fragment program once per pixel, and only "truly" supersample the depth and stencil values. (This is not the same as supersampling, but by the OpenGL 1.5 specification[2], the definition had been updated to include fully supersampling implementations as well.)

In graphics literature in general, "multisampling" refers to any special case of supersampling where some components of the final image are not fully supersampled. The lists below refer specifically to the ARB_multisample definition.



  • Pixel shader need usually be evaluated only once per pixel.
  • The edges of polygons (the most obvious source of aliasing in 3D graphics) are antialiased.


  • Aliasing and other artifacts are still visible inside rendered polygons if there are high frequency components in the fragment shader output.
  • Multi-pass rendering techniques may suffer when interacting with edges.
  • Alpha testing and fragment program discard operations will not get the benefit of multisampling.

See also


  1. ^ ARB_multisample, "Additions to Chapter 3 of the 1.2.1 specification"
  2. ^ OpenGL 1.5 specification, section F.3


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