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Feline: Fast, Elliptical Lines for Anisotropic Texture Mapping

Feline: Fast, Elliptical Lines for Anisotropic Texture Mapping. Joel McCormack, Ronald Perry, Keith I. Farkas, and Norman P. Jouppi. Outline. What should texture mapping really do? Previous work Our work: Simple Feline Image gallery Conclusions.

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Feline: Fast, Elliptical Lines for Anisotropic Texture Mapping

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  1. Feline: Fast, Elliptical Lines for Anisotropic Texture Mapping Joel McCormack, Ronald Perry, Keith I. Farkas, and Norman P. Jouppi

  2. Outline • What should texture mapping really do? • Previous work • Our work: Simple Feline • Image gallery • Conclusions

  3. An Intuitive Diagram of Texture Mapping (stolen from Landsdale) • Pixel filter is a window with variable transparency • Filter weight at a point is degree of transparency • A circular window views an elliptical texture area • Adjacent filters overlap

  4. Heckbert & Greene’s Elliptical Weighted Average (EWA) • Assume perspective distortion is constant near pixel (99.9% true) • Back mapping to screen space is a biquadratic Affine Warp Perspective Warp

  5. EWA Texturing Examples Nice definition to text without jaggies Few & faint Moiré artifacts

  6. Lance Williams’ Mip-mapping with Trilinear Filtering • Trilinear filter has (very) roughly circular contour lines, with a square footprint Affine Warp Trilinear Filter

  7. Trilinear Texturing Examples

  8. Texram (Best Case) • 2n trilinear probes along ellipse’s “major axis” • Resulting filter is too short and mesa-like at best... Texram (best case) Affine Warp

  9. Texram (Worst Case) • … and jaggedly peaked at worst. Texram (worst case) Affine Warp

  10. Texram Texturing Examples Sharp text but with jaggies (aliasing) Lots of swimming Moiré artifacts

  11. Exact Feline: Use Ellipse Parameters • n probes, Gaussian weighted, on major axis of ellipse • Important Texram problems fixed • But expensive setup comparable to EWA! Affine Warp Exact Feline

  12. Simple Feline: Approximate Ellipse • Approximate ellipse axes for cheaper setup • Slightly underestimates major radius, overestimates minor radius (resulting in fewer, fatter probes) Affine Warp Simple Feline

  13. Simple Feline: Reducing # of Probes • Allow shortening of “major axis” • Extreme sensitivity, quickly causes aliasing • 3% decrease • Allow widening probes • Causes blurring • Max of 16% (high-quality)or 31% (high-efficiency) • Allow stretching distance between probes • Causes aliasing • Max of 15% (high-quality) or 36% (high-efficiency)

  14. Simple Feline: Modest Probe Reduction • Actual blur stretch of 15.6% (maximum allowed) • Actual aliasing stretch of 7.0% Affine Warp High-Quality Simple Feline

  15. Simple Feline: “Texram Probe-Equivalent” Reduction • Actual blur stretch of 31% (maximum allowed) • Actual aliasing stretch of 26% Affine Warp High-Efficiency Simple Feline

  16. Simple Feline: “Texram Probe-Equivalent” with Gaussian Probes • Blur stretch of 36% • Aliasing stretch of 31% • Slightly blurrier, but many fewer aliasing artifacts Affine Warp High-Efficiency Feline w/Gaussian

  17. Image Gallery: Text Trilinear Texram HQ Feline EWA

  18. Image Gallery: Curves Trilinear Texram HQ Feline EWA

  19. Image Gallery: Checkerboards Trilinear Texram HQ Feline EWA

  20. Conclusions • Feline compared to EWA: • High-Quality Feline’s visual quality is comparable, using half the cycles/pixel and much smaller setup logic • Feline compared to Texram: • High-quality images far superior, using more cycles/pixel • High-efficiency images superior, using same cycles/pixel • Feline requires a tiny fraction of the die of a PC or next-generation game console graphics accelerator

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