Anti-aliasing

Aliasing

• In sound and image generation, aliasing is the generation of a false frequency along with the correct one when doing frequency sampling.
• For images, this produces a jagged edge or stair-step effect.
• For sound it produces a buzz.

Anti-aliasing

• Anti-aliasing is the smoothing of the image or sound roughness caused by aliasing.
• In image it adjust pixel positions or setting pixel intensities so that there is a more gradual transition between the color of a line and the background color.
• In sound, aliases are removed by eliminating frequencies above half the sampling frequencies.
• Anti-aliasing must be used when a gentle and blended look needed.

Types of anti-aliasing

Spatial anti-aliasing

• spatial anti-aliasing is the technique of minimizing the aliasing when representing a high-resolution image at a lower resolution.
• This is used in digital photography, computer graphics, digital audio, and many other applications.

Supersampaling(SSAA)

• In supersample anti-aliasing, multiple locations are sampled within every pixel, and each of those samples is fully rendered and combined with the others to produce the pixel that is ultimately displayed.
• This is expensive, because the entire rendering process must be repeated for each sample location.
• It is also inefficient, as aliasing is typically only noticed in some parts of the image.

Multisample(MSAA)

• In multisample anti-aliasing, if any of the multi sample locations in a pixel is covered by the triangle being rendered, a shading computation must be performed for that triangle.

Fast approximate(FXAA)

• It does not require large amounts of computing power.
• It achieves this by smoothing jagged edges according to how they appear on screen as pixels, rather than analyzing the 3D models itself as in conventional anti-aliasing.

Temporal(TAA)

• Temporal anti-aliasing seeks to reduce or remove the effects of temporal aliasing.
• Temporal aliasing is caused by the sampling rate.
• A temporal anti-aliasing filter can be applied to a camera to achieve better band-limiting.

Coverage sampling

• CSAA produces antialiased images that rival the quality of 8x or 16x MSAA, while introducing only a minimal performance hit over standard MSAA.
• It works by introducing the concept of a new sample type which is a sample that represents coverage.