# 2 then how can we solve the problem without using

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Unformatted text preview: c interpolation • Two triangles per square Questions 1. In what case hyperbolic interpolation is needed? 2. Then, how can we solve the problem without using hyperbolic interpolation? Texture Mapping & Illumination Texture mapping can be used to alter some or all of the constants in the illumination equation: • Use the texture color as the diffuse color – more natural appearance Today • Texture mapping • Antialiasing • Antialiasing textures Anti-aliasing • Aliasing: distortion artifacts produced when representing a high-resolution signal at a lower resolution. • Anti-aliasing : techniques to remove aliasing Aliased polygons (jagged edges) Anti-aliased polygons Why Does Aliasing Happen? Sampling frequency is too low with respect to the signal frequency In the example below, the pixel size is too large compared to the original scene Nyquist Limit • The signal frequency (fsignal) should be no greater than half the sample frequency (fsample) • fsignal < 0.5 fsample • In the top, fsignal = 0.8 fsample -> cannot reconstruct the original signal • In the bottom fsignal =0.5 fsample -> the original signal can be reconstructed by slightly increasing the sampling rate Wagon-wheel Effect (temporal aliasing) Anti-aliasing by Subsampling 1. 2. 3. Each pixel is subdivided (sub-sampled) into n regions Obtain the color at each subpixel Compute the average color Different Sampling Schemes Stochastic Sampling • A scene can be produced of objects that are arbitrarily small • A regular pattern of sampling will exhibit some sort of aliasing • By irregular sampling, the higher frequencies appear in the image as noise rather than aliases • Humans...
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## This document was uploaded on 03/26/2014.

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