Semi-automatic digital epigraphy from images with normals

We present a semi-automated system for converting photometric datasets (RGB images with normals) into geometry-aware non-photorealistic illustrations that obey the common conventions of epigraphy (black-and-white archaeological drawings of inscriptions). We focus on rock inscriptions formed by carving into or pecking out the rock surface: these are characteristically rough with shallow relief, making the problem very challenging for previous line drawing methods. Our system allows the user to easily outline the inscriptions on the rock surface, then segment out the inscriptions and create line drawings and shaded renderings in a variety of styles. We explore both constant-width and tilt-indicating lines, as well as locally shape-revealing shading. Our system produces more understandable illustrations than previous NPR techniques, successfully converting epigraphy from a manual and painstaking process into a user-guided semi-automatic process.