AntiAliasing

1
Anti-Aliasing
Methods

• Super Sampling
• Multiple sample points across a finer grid to
  determine pixel intensity
• High Resolution Computation
• Low Resolution display
• Obtain intensity information from multiple points
  that contribute to intensity of pixel.
• Run Bresenhams algorithm on microgrid.
• Set pixel intensities

• Aliasing
• Distortion of information due to low frequency
  sampling
• Under sampling
• Anti-aliasing
• Compensates for this distortion
• If pixels have more than one intensity
• Vary the intensity levels to compensate

2
SuperSampling

• Plot (0,0 to 2,1)
• ?x 2, ?y 1
• Multiply both directions by 3 (adding a 3x3 grid)
• Plotting (microgrid)
• ?x 8, ?y 4
• P0 2?y ?x 0

0 0
K PK XK1 YK1 0 0 1 1 1 -8
2 1 2 0 3 2 3 -8 4 2 4
0 5 3 5 -8 6 3 6 0 7
4 7 -8 8 4
If PK lt 0 plot XK1, YK PK1
PK 2?y Else plot XK1, YK1 PK1 PK
2?y -2?x
3
Anti-aliasingNormal weighting
Anti-aliasingWeighted
1/3
1
7
2/3
7
3

• At most 3 micro-pixels filled
• 4 levels of intensity (including off)
• 3 full, 2 2/3, 1 1/3, 00