We present a practical method of visualizing and enhancing the appearance of surface structure. Multiple images of a surface are collected from a fixed viewing position, but varying lighting directions. For each pixel, a low-order model is fit to the resultant color or luminance variation. Coefficients of a biquadratic polynomial are stored per pixel, and used to interactively reconstruct the surface color under varying lighting conditions. Like bump mapping, this allows the perception of surface deformations. Unlike bump maps, these Polynomial Texture Maps (PTMs) also capture variations due to surface self-shadowing and interreflections, which enhance realism. We have also found PTMs useful for producing a number of other effects such as anisotropic and Fresnel shading models and variable depth of focus. Lastly, we present several reflectance function transformations that act as contrast enhancement operators. This new class of contrast enhancement can be used in conjunction with existing 2D methods such as histogram equalization and high pass filtering. We have found this method particularly useful in the study of ancient archeological clay and stone writings, forensics and paleontology.
Copyright. All Rights Reserved.