1 Extracting Scar and Ridge Features from 3D-scanned Lithic Artifacts Eitan Richardson 1) , Leore Grosman 2) , Uzy Smilansky 2) and Michael Werman 1) The Hebrew University, Jerusalem, Israel 1) Department of Computer Science. 2) Computerized Archaeology Laboratory, The Institute of Archaeology. Abstract We propose a method for computer analysis of 3D-scanned lithic artifacts. It provides a detailed description of the scars and ridges that were left on the surface of the stone tool while it was produced by knapping. Traditional documentation and research methods are based on hand drawn images of stone tools and manual measurements. Our algorithm enables automatic, objective and precise documentation of the tool surface, together with a quantitative analysis of the scar and the ridge networks. The proposed algorithm detects ridges on the surface of the scanned object, segments the surface to scars and calculates features that can be used for clustering and classifying lithic artifacts. We demonstrate our method on various lithic artifacts, present the extracted features and compare the results to traditional hand drawings. 1. Introduction Much of what is known today about prehistoric periods derives from the study of stone artifacts manufactured during the Paleolithic period that spans over 99.5% of human history. The gradual evolution of stone technology from rough and simple forms to highly sophisticated and refined objects marks the cognitive evolution of the human brain, as well as the development of manual, technical and social skills. Prehistoric stone tools were manufactured by knapping flakes from a stone core and creating a scared surface. The surface that is created after removing a flake is called a scar and the boundary of the scar a ridge. As more flakes are removed, ridges become borders between adjacent scars on the lithic artifact (Figure 1). Figure 1: Lower Paleolithic Handaxe from the site NBA (after Grosman et al 2011). (a) A photograph of the stone tool (b) A traditional hand drawing with indication of a scar and a ridge (c) Rendering of the 3D-scanned tool