Lecture06-Anti-Aliasing

Lecture06-Anti-Aliasing - CS 455 Computer Graphics...

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CS 455 – Computer Graphics Antialiasing
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Aliasing Aliasing: a high-frequency signal masquerading as a low frequency Caused by insufficient sampling (sampling interval too large) Sampling Interval Actual (high-frequency) signal Sampled (aliased) signal
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Strobe light on dripping water: Temporal aliasing Spokes on a rotating wheel: Temporal aliasing Moiré patterns: Spatial aliasing Examples of Aliasing
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Aliasing and Line Drawing We draw lines by sampling at intervals of one pixel and drawing the closest pixels Sampling Interval Sampling Interval Results in stair-stepping (i.e., the dreaded “jaggies”)
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Antialiasing Lines Idea: Make line “fatter” Fade line out (removes high frequencies) Now sample the line
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Antialiasing Lines Solution 1 – Unweighted Area Sampling: Treat line as a single-pixel wide rectangle Color pixels according to the percentage of each pixel that is “covered” by the rectangle
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Solution 1: Unweighted Area Sampling Pixel area is unit square Constant weighting function Pixel color is determined by computing the amount of the pixel covered by the line, then shading accordingly Easy to compute, gives reasonable results Line One Pixel
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This note was uploaded on 03/02/2012 for the course C S 455 taught by Professor Jones,m during the Winter '08 term at BYU.

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Lecture06-Anti-Aliasing - CS 455 Computer Graphics...

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