Polynomial Texture Maps

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Polynomial Texture Maps

• Dan Hazen

CS 395 Advanced Computer Graphics January 22,
2002
Based on the paper
Malzbender, T., Gelb, D., Wolters, H.,
Polynomial Texture Maps, Computer Graphics
(SIGRAPH 01 PROCEEDINGS), August 2001.
www.hpl.hp.com/ptm
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Introduction
What are Polynomial Texture Maps (PTMs)? Image
based texture maps used for more accurate
texturization of fine details.
Why use PTMs? More Realistic Textures!
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Background
Bi-directional Texture Function
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Background
Bi-directional Texture Function (Cont.)
Conventional
Conventional
BTF
BTF
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Polynomial Texture Mapping
Store coefficients at EACH TEXEL. Coefficients
derived from series of photographs.
L(u,v) a0(u,v)lu2 a1(u,v)lv2
a2(u,v)lulv a3(u,v)lu
a4(u,v)lv a5(u,v)
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Polynomial Texture Mapping (Cont.)
DEMO!
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Polynomial Texture Mapping (Cont.)
Capture images using devices to get the
coefficients
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Polynomial Texture Mapping (cont.)
Storage Concerns
Best Case
Worst Case
500x500 Image 2.2 Megs
500x500 Image 5.1 Megs
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PTM Applications
Specular Highlighting
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PTM Applications (Cont.)
Contrast Enhancement Method 1 Specular
Highlights
Original Photo
PTM Reconstruction
Specular Highlight
PTM Highlight
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PTM Applications (Cont.)
Contrast Enhancement Method 2 Diffuse Gain
Original Photograph
Diffuse Gain 1.9
PTM Reconstruction
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PTM Applications (Cont.)
Contrast Enhancement Method 3 Light
Extrapolation
Original Photograph
Extrapolated PTM Reconstruction
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PTM Applications (Cont.)
Video http//www.hpl.hp.com/ptm/
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PTM Applications (Cont.)
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PTM Applications (Cont.)
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PTM Applications (Cont.)
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PTM Applications (Cont.)
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PTM Applications (Cont.)
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PTM Applications (Cont.)
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PTM Advantages and Issues

• Advantages
• 1. Only images needed to form the texture
• 2. Texture maps maintain roughness
• 3. Neat lighting and viewing tricks
• 4. Efficient enough for interactive speeds once
  coefficients are obtained

• Issues
• 1. Storage Costs
• 2. Using biquadratic polynomial in some cases
  may not be precise enough

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PTM Research Expansion
Suggestions for research expansion

• Use a higher order polynomial for better
  representation
• Use basis functions to reduce storage costs
• Get rid of fixed camera constraint to get a
  higher number of free dimensions
• Add modeling surface opacity to the list of
  features

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Conclusions

• Polynomial Texture Maps (PTMs) portray rough
  surfaces based on a set of input images
• Polynomial Texture Maps can be used for more than
  just interactively moving a light source around a
  texture there are methods that improve image
  definition
• Easy to do in hardware but storage could be a
  problem

QUESTIONS?