3D Surface Measurement and Analysis of Works of Art

Surface shape metrology encompasses broad topics within cultural heritage science. However, most existing surface shape measurement systems are bulky and restricted to lab environments. As most are not practical for large, delicate or fixed works of art, such as stained-glass windows or oil-painted murals, we develop methods to measure matte and specular surfaces using hand-held mobile devices. In the `Shape-from-Shifting' method, we use a hand-held cell-phone to capture surface normal maps computed with a near-light variant of photometric stereo from a shifting sequence of flash-lit photos. In the `Multiview Deflectometry' method, 3D information of specular surfaces is calculated by observing the reflection of a tablet screen on the surface with the tablet's front facing camera. Both methods are fast, portable and easy to use for non-experts. We present case studies for each method: detecting protrusions growing in Georgia O'Keeffe paintings and identifying surface features of Tiffany stained glass.