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Anti-aliasing may refer to any of a number of techniques to combat the problems of
aliasing In signal processing and related disciplines, aliasing is a phenomenon that a reconstructed signal from samples of the original signal contains low frequency components that are not present in the original one. This is caused when, in the ori ...
in a sampled signal such as a
digital image A digital image is an image composed of picture elements, also known as pixels, each with '' finite'', '' discrete quantities'' of numeric representation for its intensity or gray level that is an output from its two-dimensional functions f ...
or
digital audio Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...
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 Computer-generated imagery (CGI) is a specific-technology or application of computer graphics for creating or improving images in Digital art, art, Publishing, printed media, Training simulation, simulators, videos and video games. These images ...
(CGI), the application of computer graphics for creating or improving images in art, printed media, simulators, videos and video games. *
Spatial anti-aliasing In digital signal processing, spatial anti-aliasing is a technique for minimizing the distortion artifacts (aliasing) when representing a high-resolution image at a lower resolution. Anti-aliasing is used in digital photography, computer graphics ...
, 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 Nvidia Corporation ( ) is an American multinational corporation and technology company headquartered in Santa Clara, California, and incorporated in Delaware. Founded in 1993 by Jensen Huang (president and CEO), Chris Malachowsky, and Curti ...
. May also be referred to as Fast Sample Anti-aliasing (FSAA). **
Multisample anti-aliasing Multisample anti-aliasing (MSAA) is a type of spatial anti-aliasing, a technique used in computer graphics to remove jaggies. It is an optimization of supersampling, where only the necessary parts are sampled more. Jaggies are only noticed in ...
(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 * Spatio-temporal anti-aliasing, which addresses spatial aliasing using information from other time samples **
Temporal anti-aliasing Temporal anti-aliasing (TAA), also known as TXAA (a proprietary technology) or TMAA/TSSAA (''Temporal Super-Sampling Anti-Aliasing''), is a spatial anti-aliasing technique for computer-generated video that combines information from past frames and ...
(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 Here may refer to: Music * ''Here'' (Adrian Belew album), 1994 * ''Here'' (Alicia Keys album), 2016 * ''Here'' (Cal Tjader album), 1979 * ''Here'' (Edward Sharpe album), 2012 * ''Here'' (Idina Menzel album), 2004 * ''Here'' (Merzbow album), ...
. 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.Grant, C. (1985)
"Integrated analytic spatial and temporal anti-aliasing for polyhedra in 4-space"
'' SIGGRAPH Computer Graphics'', 19(3):79-84
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.Tessive, LLC (2010)
"Time Filter Technical Explanation "
/ref> A common example of temporal aliasing in film is the appearance of vehicle wheels travelling backwards, the so-called
wagon-wheel effect The wagon-wheel effect (alternatively called stagecoach-wheel effect) is an optical illusion in which a spoked wheel appears to rotate differently from its true rotation. The wheel can appear to rotate more slowly than the true rotation, it ca ...
.


In cel animation

In
cel animation Traditional animation (or classical animation, cel animation, or hand-drawn animation) is an animation technique in which each frame is drawn by hand. The technique was the dominant form of animation of the 20th century, until there was a shif ...
, 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 Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or l ...
*
Exposure (photography) In photography, exposure is the amount of light per unit area reaching a frame (photography), frame of photographic film or the surface of an electronic image sensor. It is determined by shutter speed, lens f-number, and scene luminance. Exposure ...
*
Temporal posterization Posterization or posterisation of an image is the conversion of a continuous gradation of tone to several regions of fewer tones, causing abrupt changes from one tone to another. This was originally done with photographic processes to create ...


References

Anti-aliasing algorithms


See also

*
Aliasing In signal processing and related disciplines, aliasing is a phenomenon that a reconstructed signal from samples of the original signal contains low frequency components that are not present in the original one. This is caused when, in the ori ...
*
Pixel-art scaling algorithms Pixel art scaling algorithms are graphical filters that attempt to enhance the appearance of hand-drawn 2D pixel art graphics. These algorithms are a form of automatic image enhancement. Pixel art scaling algorithms employ methods significantly ...
*
Nyquist–Shannon sampling theorem The Nyquist–Shannon sampling theorem is an essential principle for digital signal processing linking the frequency range of a signal and the sample rate required to avoid a type of distortion called aliasing. The theorem states that the sample r ...


References

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