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Aliasing
Antialiasing

(Terms of computer graphics)

When a line in a digital image runs at an angle, then it will often appear with jagged edges. This effect is caused by the regular pixel grid in the image, and is called aliasing.

Illustration of aliasing/antialiasing
Example of aliased and antialiased line.

To avoid this effect, the process of antialiasing paints some nearby pixels in an intermediate color or brighness. That way, the visuall appearance of the line (or an edge) is smoothed out.

The problem of aliasing is prevalent in synthetic images created by methods such as raytracing. Some programs try to circumvent it by sending more than one ray per pixel (oversampling), and interpolating their result. With the Radiance software, the same result is reached by rendering an image that is two or three times as big as the target size with rpict(1), and then filtering this intermediate image down to scale with pfilt(1). To get even smoother results, the image can also be rendered with jittered sampling.

 

References:
   image filtering
jittered sampling
Radiance_software
raytracing
 
 
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aliasing    Das Aliasing
antialiasing    Das Antialiasing
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