Anti-aliasing

Anti-aliasing may refer to any of a number of techniques to combat the problems of aliasing in a sampled signal such as a digital image or digital audio recording.

Specific topics in anti-aliasing include:

• Anti-aliasing filter, a filter used before a signal sampler to restrict the bandwidth of a signal such as in audio applications.
• Manual anti-aliasing, an artistic technique done in pixel art graphics to smooth transitions between shapes, soften lines or blur edges.
• Computer-generated imagery (CGI), the application of computer graphics for creating or improving images in art, printed media, simulators, videos and video games.^[1]

• Spatial anti-aliasing, the technique of minimizing aliasing when representing a high-resolution image at a lower resolution
  • Fast approximate anti-aliasing (FXAA), an anti-aliasing algorithm created by Timothy Lottes under Nvidia. May also be referred to as Fast Sample Anti-aliasing (FSAA).
  • Multisample anti-aliasing (MSAA), a type of spatial anti-aliasing method
  • Super-sampling (SSAA), a type of spatial anti-aliasing method
  • Morphological antialiasing (MLAA), a type of spatial anti-aliasing method
  • Conservative morphological anti-aliasing (CMAA), a type of spatial anti-aliasing method^[2]
• Spatio-temporal anti-aliasing, which addresses spatial aliasing using information from other time samples
  • Temporal anti-aliasing (TAA) in CGI, techniques to reduce or remove the effects of spatial aliasing in moving images by using pixel information from previous time samples
• Spatial and temporal anti-aliasing
  • Deep learning anti-aliasing (DLAA), a type of spatial and temporal anti-aliasing method relying on dedicated tensor core processors
  • Deep learning super sampling (DLSS), a family of real-time deep learning image enhancement and upscaling technologies developed by Nvidia that are available in a number of video games.

Temporal anti-aliasing

Temporal anti-aliasing has two meanings. It is currently commonly and widely used to describe a technique for realtime spatial anti-aliasing, usually in computer and video games, described in detail here. It is also formally used to describe techniques for reducing aliasing in the time dimension - that is, aliasing due to under-sampling in the time dimension. Temporal aliasing in video applications is caused by the sampling rate (i.e. number of frames per second) of a scene being too low compared to the transformation speed of objects inside of the scene; this causes objects to appear to jump or appear at a location instead of giving the impression of smoothly moving towards it. To avoid aliasing artifacts, the sampling rate of a scene must be at least twice as high as the fastest moving object.^[3] The shutter behavior of the sampling system (typically a camera) strongly influences aliasing, as the overall shape of the exposure over time determines the band-limiting of the system before sampling, an important factor in aliasing. A temporal anti-aliasing filter can be applied to a camera to achieve better band-limiting.^[4] A common example of temporal aliasing in film is the appearance of vehicle wheels travelling backwards, the so-called wagon-wheel effect.

In cel animation

In cel animation, animators can either add motion lines or create an object trail to give the impression of movement. To solve the wagon-wheel effect without changing the sampling rate or wheel speed, animators could add a broken or discolored spoke to force viewer's visual system to make the correct connections between frames.

See also

• Motion blur
• Exposure (photography)
• Temporal posterization