Polynomial Texture Mapping / Reflectance Transformation Imaging

Polynomial Texture Mapping, or PTM for short, is part of the family of technologies known as Reflectance Transformation Imaging (RTI). RTI approaches have for the last ten years been traditionally used to create interactive images of objects, whereby the user is presented with a photograph of an object whose illumination can be altered at will on screen. This 'interactive relighting' of objects can be incredibly powerful in revealing the detail of a surface. Because the technique captures the surface normal in addition to colour information, a variety of powerful filters can be used to enhance the surface, even removing colour information entirely. RTI techniques are being used within the cultural heritage sector to help read cuneiform tablets, illuminated manuscripts, interpret rock art, read eroded inscriptions, and examine glazes, to name but a few of its applications.
 
These techniques can also be used to investigate whole landscapes by transferring the technique to a virtual world. Using virtual objects captured using Airborne Laser Scanning (ALS), Terrestrial Laser Scanning (TLS) or Close Range Laser Scanning (CRLS) techniques, combined with virtual lights and virtual cameras, it is possible to generate the same sorts of interactive outputs as with real objects, lights and cameras.

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Case Studies