What is Anti-Aliasing?
Aliasing is an effect that causes different signals to become indistinguishable when sampled in computer graphics. It refers to the distortion resulting from a signal reconstructed from samples different from the original continuous signal. Aliasing effects are known as scan conversion side effects because they are produced when objects are mapped to discrete approximations from their defined continuous space through scan conversion.
Aliasing is a jagged edge that occurs in an image. It is also referred to as jaggies. Jaggies appear because the images are displayed using rectangular pixels, and often when curves or rounded shapes need to be displayed, these rectangular pixels are not able to define the edges smoothly. Due to poor pixelation, the figures don’t appear well-defined. Let us look at an image with jaggies to understand what we mean when we say that we cannot get smooth edges through rectangular pixels.

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Anti-aliasing is a graphics technique for smoothing jagged edges or lines by surrounding the jaggies with transparent pixels to simulate the appearance of fractionally-filled pixels.
The technique works by sampling the pixels around the edges of an image. By using colours that it samples, anti-aliasing blends away the appearance of jagged edges.
What are the different types of anti-aliasing techniques?
Anti-aliasing techniques are categorized into two types:
- Spatial anti-aliasing
- Post-process anti-aliasing
Spatial Anti-aliasing
In this technique, lower resolution images are rendered at a higher resolution and at high resolution, colour samples are taken of the excess pixels. The high-resolution of the image is shrunk down to the original resolution, and each pixel receives a new colour that’s averaged from the sampled pixels.

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Different types of spatial anti-aliasing techniques are as follows:
Supersampling anti-aliasing: It is a full-scene method as it requires that the entire image must be processed before the jaggies can be smoothed. It softens the sharp lines that appear in the image and may negatively affect the images with lots of horizontal and vertical lines.

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Multisample anti-aliasing: In this method, only the edges of the detected polygons in the image are smoothed out and it does not work on the textures in the image.

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Post-process anti-aliasing
In post-process anti-aliasing, each pixel is slightly blurred after rendering. The GPU determines the location of the edge of a polygon by comparing the colour contrast between each two pixels - two similar pixels indicate that they’re part of the same polygon. Then, the pixels are blurred proportionally according to their contrast.
Blurring is an effective method because it eliminates the stark contrast between awkwardly aligned pixels that are causing jaggies.
Temporal anti-aliasing and morphological anti-aliasing are the kinds of methods that fall under this category. These methods focus on blurring the jagged portions of the image and then super sampling them to produce anti-aliasing effects.
Morphological anti-aliasing detects borders in the resulting image and finds the patterns in those and blends them together.

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While, temporal anti-aliasing samples each pixel once per frame but in different locations. Then the samples in past frames are blended with pixels in the current frame to produce the final image.

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