Morphological antialiasing


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Morphological antialiasing

  1. 1. Morphological AntialiasingAuthor:Alexander ReshetovIntel LabsSpeaker: 李仲元
  2. 2. Outline Introduction Previous method ◦ Super Sampling Anti-Aliasing (SSAA) ◦ Multi Sampling Anti-Aliasing (MSAA) Morphological Anti-Aliasing (MLAA) ◦ Black-and-white image ◦ Color image Experiment Reference ◦ Sub-pixel Reconstruction Anti-Aliasing (SRAA)
  3. 3. Introduction Anti-aliasing Call of Duty: World at War
  4. 4. Previous method Full scene Anti-aliasing avoid aliasing on full-screen images Super-Sampling Anti-aliasing MultiSampling Anti-Aliasing CoverageSampling Anti-Aliasing Custom Filter Anti-Aliasing
  5. 5. Previous method - SSAA Upscale image to higher resolution Then downsampling it to the desired size Brute-Force method
  6. 6. Previous method - MSAA Like SSAA, but just do super-sampling for Z-buffer and Stencil Buffer Assume that the change of color in one pixel is not obvious Disadvantages : ◦ If the alpha value of a translucent fragment is not within a specified range, it will be discarded after alpha testing
  7. 7. Previous method - MSAA
  8. 8. Previous method Different Sampling method will affect the result High quality result with high cost Must combine with forward rendering
  9. 9. Morphological Anti-Aliasing Algorithm for black-and-white implementation ◦ Step 1: Separate different color area ◦ Step 2: Classify separation line ◦ Step 3: Compute new color for cells
  10. 10. Step 1: Separate Assume that border pixels are extended into additional imaginary rows and columns
  11. 11. Step 2: Classify Look for other separation lines which are orthogonal to the current one at its farthest vertices A single separation line can be a part of multiple patterns (up to four) classify separation lines into the following three categories: ◦ 1. Z-shaped pattern ◦ 2. U-shaped pattern ◦ 3. L-shaped pattern
  12. 12. Step 2: Classify
  13. 13. Step 3: Compute I) Anti-aliasing area Z and U shapes can be split into two L- shapes Substep 1. consider each L-shape to be formed by a primary edge found at the first step, secondary edge found at the second step
  14. 14. Step 3: Compute
  15. 15. Step 3: Compute Substep 2. Connect the middle point of the secondary edge with the remaining vertex of the primary edge
  16. 16. Step 3: Compute
  17. 17. Step 3: Compute II) Computing blending weights We calculate the area of each trapezoid attached to the primary edge and use it to compute new color of these cells as follows:
  18. 18. Step 3: Compute c5 = 1/3*0 + 2/3*1 d5=1/24*0 + 23/24*1
  19. 19. Step 3: Compute
  20. 20. Morphological Anti-Aliasing Algorithm for color image ◦ Step 1: Found discontinuities in color image ◦ Step 2: Classify separation line ◦ Step 3: Pattern search Optimization Limitation Feature
  21. 21. Step 3: Pattern search
  22. 22. Step 3: Pattern search Can use different method to get answers ◦ Solve the equation for each channel, then average the solution ◦ Summing all values to form a single numerical value(assign different weights to different channels, deferring more advanced luminance processing until GPU implementation) If the found values of hc and hd are in the [0, 1] interval, we process the tested shape, otherwise ignore it
  23. 23. Morphological Anti-Aliasing Feature ◦ MLAA can be used for any image processing task and does not use any data besides color values ◦ Can combine with deferred rendering, allowing for better processor utilization ◦ The algorithm achieves reasonable performance without any noticeable impact ◦ The “best in class” approach for anti-aliased deferred shading before Feb, 2011
  24. 24. Morphological Anti-Aliasing Optimization ◦ searching for color discontinuities  Each RGBA color requires 32 bits, so 4 RGBA pixels will fit into one SSE register Limitation ◦ Running time depends on number of edges  For the CPU version of MLAA, processing about 20M pixels per second on a single 3GHz core ◦ Can’t respect geometric boundaries well
  25. 25. Experiment Top row: bitmap font; Second row: TrueType font (antialiased) Third row: MLAA processing of bitmap font Ffourth row: MLAA processingof TrueType font. Font size from left to right: 24, 12, 8, and 6
  26. 26. Experiment
  27. 27. Reference - SRAA Subpixel Reconstruction Antialiasing for Deferred Shading ◦ Matthäus G. Chajdas, Morgan McGuire, David Luebke ◦ ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games 2011
  28. 28. Reference - SRAA An efficient algorithm for antialiasing images as a post-process Increase performance for small quality reductions Detailed analysis of the algorithm and comparison to MLAA Evaluation on real game scenes including texture, specular reflection, geometric aliasing, emission, and bloom
  29. 29. Reference - SRAA