Reflectance Transformation Imaging

One of the techniques that I was able to use during my curatorial internship in the Bryn Mawr Special Collections last spring was Reflectance Transformation Imaging (also known as polynomial texture mapping). The technique uses an algorithm to reconstruct the surface normals of an object based on changes in illumination position. That I was able to use this technique at all is thanks to the non-profit Cultural Heritage Imaging project’s excellent tutorials, as well as to funding for equipment from Bryn Mawr College Special Collections.

I haven’t blogged about my use of this technology, however, because until this point it has been somewhat awkward to share RTI files online. Possible solutions involved either sharing the RTI files directly (placing the burden on others to install the RTI viewer software) or java plugins, such the excellent RTI viewer WordPress plugin. Neither is particularly elegant.

That’s why I’m so thrilled that Gianpaolo Palma has released the code for his WebGL-based RTI viewer, which neatly combines an RTI-Viewer with a tile-based deep-zoom. I’ll be putting up some of the coin RTI’s that I made as soon as I get the chance to process them on a windows machine.