The photographic study and illustration of fossil specimens often involves enhancement of contrast. This contrast can be achieved with a number of photographic techniques such as oblique lighting, immersion in a liquid, and the use of polarized or ultraviolet light or high-contrast film (Howell 1977; Conway Morris 1985; Rayner 1992; Boyle 1992; Bengtson 2000). More recently, these techniques have been augmented by digital contrast-enhancement algorithms such as sharpening, filtering, and edge detection (Kirschvink et al. 1982; Ekdale and Jeong-Kyungwan 1996; Bengtson 2000). Digital image enhancement of paleontological photographs has so far involved the transformation of a single captured image. Such an image represents a blending of color, reflectance, and shading information in one two-dimensional image. The amount of enhancement possible is therefore severely limited. By combining a number of images made with different directions of incoming light, it is possible to record the luminance of each pixel under a variety of lighting situations. By converting this information through a suitable algorithm, a dynamic texture map can be rendered that allows the simulation of the surface being seen under all conceivable (and some inconceivable!) lighting conditions. The method, Polynomial Texture Mapping (PTM), allows the user to apply virtual light sources to a three-dimensional surface and to manipulate the color and reflectance properties of the surface (Malzbender et al. 2000, 2001).

This principle has been put to use in the study of partly effaced script on archeological artifacts and other objects (Malzbender et al. 2000, 2001; Brooks 2001), and a number of other applications are being tested. The study and illustration of fossil specimens appears to be a field where the method shows particular promise. In addition to the possibility of revealing subtle structures that may otherwise be difficult to illustrate, PTM lends itself nicely to interactive presentation, allowing manipulation of virtual light sources as well as surface properties. It therefore enables the production of images for electronic publication, allowing the reader to choose the optimal lighting and surface properties for studying different structures in the object.

We describe here the PTM method and explore its use for different kinds of fossils having varying relief, color and reflectance. As anticipated, some types of structures respond better than others to this kind of image manipulation, but in all cases visualization of fossils is enhanced by providing readers with the opportunity for interactive image manipulation.