Polynomial Texture Map
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Polynomial Texture Mapping (PTM) is a new method for increasing the photorealism of texture maps. Coefficients of a biquadratic polynomial are stored per texel, and used to reconstruct the surface color under varying lighting conditions.
Like bump mapping, this allows the perception of surface deformations. However, our method is image based, and photographs of a surface under varying lighting conditions can be used to construct these maps.
Unlike bump maps, Polynomial Texture Maps (PTMs) also capture variations due to surface self-shadowing and interreflections, which enhance realism. Surface colors can be efficiently reconstructed from polynomial coefficients and light directions with minimal fixed-point hardware.
We have also found PTMs useful for producing a number of other effects such as anisotropic and Frensel shading models and variable depth of focus. Lastly, we have discovered several reflectance function transformations that act as contrast enhancement operators.