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Feline: Fast, Elliptical Feline: Fast, Elliptical Lines for Anisotropic Lines for Anisotropic Texture MappingTexture Mapping

Joel McCormack, Ronald Perry, Joel McCormack, Ronald Perry, Keith I. Farkas, and Norman P. Keith I. Farkas, and Norman P. JouppiJouppi


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OutlineOutlineWhat should texture mapping really do?Previous workOur work: Simple FelineImage galleryConclusions


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An Intuitive Diagram of An Intuitive Diagram of Texture Mapping (stolen Texture Mapping (stolen from Landsdale)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


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Heckbert & Greene’s Heckbert & Greene’s Elliptical Weighted Average Elliptical Weighted Average (EWA)(EWA)

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Assume perspective distortion is constant near pixel (99.9% true)

Back mapping to screen space is a biquadraticPerspective Warp Affine Warp


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EWA Texturing ExamplesEWA Texturing Examples

Few & faint Moiré artifacts

Nice definition to text without jaggies


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Lance Williams’ Mip-Lance Williams’ Mip-mapping with Trilinear mapping with Trilinear FilteringFiltering

Trilinear filter has (very) roughly circular contour lines, with a square footprint

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Affine Warp Trilinear Filter


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Trilinear Texturing Trilinear Texturing ExamplesExamples

Ellipticalfootprint

Trilinearfootprint

Ellipticalfootprint

Trilinearfootprint


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

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Affine WarpTexram (best case)


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Texram (Worst Case) Texram (Worst Case) … and jaggedly peaked at worst.

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Affine WarpTexram (worst case)


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Texram Texturing ExamplesTexram Texturing Examples

Lots of swimming Moiré artifacts

Sharp text but with jaggies (aliasing)


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Exact Feline: Use Ellipse Exact Feline: Use Ellipse ParametersParameters

n probes, Gaussian weighted, on major axis of ellipseImportant Texram problems fixedBut expensive setup comparable to EWA!

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Affine Warp

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Exact Feline


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Simple Feline: Approximate Simple Feline: Approximate EllipseEllipse

Approximate ellipse axes for cheaper setupSlightly underestimates major radius, overestimates minor radius (resulting in fewer, fatter probes)

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Affine Warp Simple Feline


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Simple Feline: Reducing # Simple Feline: Reducing # of Probesof Probes

Allow shortening of “major axis”Extreme sensitivity, quickly causes aliasing3% decrease

Allow widening probesCauses blurringMax of 16% (high-quality)or 31% (high-efficiency)

Allow stretching distance between probesCauses aliasingMax of 15% (high-quality) or 36% (high-efficiency)


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Simple Feline: Modest Simple Feline: Modest Probe ReductionProbe Reduction

Actual blur stretch of 15.6% (maximum allowed)Actual aliasing stretch of 7.0%

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Affine Warp High-Quality Simple Feline


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Simple Feline: “Texram Simple Feline: “Texram Probe-Equivalent” Probe-Equivalent” ReductionReduction

Actual blur stretch of 31% (maximum allowed)Actual aliasing stretch of 26%

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Affine Warp High-Efficiency Simple Feline


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Simple Feline: “Texram Simple Feline: “Texram Probe-Equivalent” with Probe-Equivalent” with Gaussian ProbesGaussian Probes

Blur stretch of 36%Aliasing stretch of 31%

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Affine Warp High-Efficiency Feline w/Gaussian

Slightly blurrier, but many fewer aliasing artifacts


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Image Gallery: TextImage Gallery: Text

HQ Feline EWA

Trilinear Texram


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Image Gallery: CurvesImage Gallery: Curves

EWAHQ Feline

Trilinear Texram


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Image Gallery: Image Gallery: CheckerboardsCheckerboards

HQ Feline EWA

Trilinear Texram


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ConclusionsConclusionsFeline 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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