During a visit to HP labs in Palo Alto a possible new approach to Raking Light examinations was discussed, Polynomial Texture Mapping (PTM). PTM is a process by which maps of the surface texture of an object can be recorded and easily displayed.
Very briefly, it works by capturing multiple images, each lit from a different direction, of a stationary object. This process records all of the shadows cast across the surface of the object when it is lit from different directions. This set of images and a record of the relative positions of each of the lights are then used to calculate the surface texture of the object as a PTM file.
When the PTM file is viewed on the computer the virtual light source illuminating the screen can be rotated around the object, showing up all of the surface texture. This gives you the virtual equivalent of picking up your object and moving it about under a strong directional light.
In addition to simply moving the virtual light source, the information stored within the texture map allows the user to alter the virtual surface properties of an object, effectively altering the gloss and reflective properties of the surface. This can allow even more details of the surface texture of an object to be revealed.
Polynomial Texture Mapping (PTM) has been developed at HP labs in Palo Alto by Tom Malzbender and Dan Gelb, details of the PTM process and the software required to test the system is available from the HP lab PTM web site. Example PTMs and some to the relevant literature is also available from the PTM web site.