CMSC 435
Antialiasing
Aliasing
Visual artifactsjagged lines and edges
high frequencies appearing as lowsmall objects missedtexture distortions
strobing and poppingbackward movement
Rendering Process
Two basic stagessamplingreconstruction
Assuming discrete sampling
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
Sampling Schemes
Regular supersamplingJittered supersamplingAdaptive supersamplingStochastic sampling
Reconstruction
Reconstruction: recreate a continuoussignal from a set of samplesTasks of reconstruction filter
remove extraneous replicas of signalspectrum
pass the original signal base unchanged