antialiasing - department of computer science and electrical...
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CMSC 435
Antialiasing
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Aliasing
Visual artifactsjagged lines and edges
high frequencies appearing as lowsmall objects missedtexture distortions
strobing and poppingbackward movement
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Rendering Process
Two basic stagessamplingreconstruction
Assuming discrete sampling
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Sampling Theory
Shannon s sampling theory (1D):A band limited signal f(t) with cut off frequency wFmay be perfectly reconstructed from its samplesf(nT0) if 2 /T0 >= 2wF
wF == Nyquist limit
Alternatively:a signal can be reconstructed exactly fromsamples only if the highest frequency is less thanhalf the sampling rate
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Sampling Schemes
Regular supersamplingJittered supersamplingAdaptive supersamplingStochastic sampling
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Reconstruction
Reconstruction: recreate a continuoussignal from a set of samplesTasks of reconstruction filter
remove extraneous replicas of signalspectrum
pass the original signal base unchanged
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