Practical and technical aspects for the 3D scanning of lithic artefacts using micro-computed tomography techniques and laser light scanners for subsequent geometric morphometric analysis. Introducing the StyroStone protocol

Abstract

Here, we present a new method to scan a large number of lithic artefacts using three-dimensional scanning technology. Despite the rising use of high-resolution 3D surface scanners in archaeological sciences, no virtual studies have focused on the 3D digitization and analysis of small lithic implements such as bladelets, microblades, and microflakes. This is mostly due to difficulties in creating reliable 3D meshes of these artefacts resulting from several inherent features (i.e., size, translucency, and acute edge angles), which compromise the efficiency of structured light or laser scanners and photogrammetry. Our new protocol StyroStone addresses this problem by proposing a step-by-step procedure relying on the use of micro-computed tomographic technology, which is able to capture the 3D shape of small lithic implements in high detail. We tested a system that enables us to scan hundreds of artefacts together at once within a single scanning session lasting a few hours. As also bigger lithic artefacts (i.e., blades) are present in our sample, this protocol is complemented by a short guide on how to effectively scan such artefacts using a structured light scanner (Artec Space Spider). Furthermore, we estimate the accuracy of our scanning protocol using principal component analysis of 3D Procrustes shape coordinates on a sample of meshes of bladelets obtained with both micro-computed tomography and another scanning device (i.e., Artec Micro). A comprehensive review on the use of 3D geometric morphometrics in lithic analysis and other computer-based approaches is provided in the introductory chapter to show the advantages of improving 3D scanning protocols and increasing the digitization of our prehistoric human heritage.

The contribution of integrated 3D model analysis to Protoaurignacian stone tool design

“…Particularly, the combination of global shape description with specific features of stone tool variability, such as cross-section outline and retouch angle, is particularly effective in quantifying differences in the technological procedures used to produce and further modify stone tools. The effectiveness of the new StyroStone scanning protocol [ 58 , 68 ] combined with open-source software to conduct shape assessments, such as AGMT3-D [ 53 ], will certainly facilitate future studies and provide additional evidence. This can be eventually compared with the results achieved at Fumane Cave thanks to the open-access repository containing all 3D meshes analyzed in this study [ 75 ].…”

“…The bigger blades (n = 132) were instead scanned with an Artec Spider (EVA-D-3D) structured light surface scanner and the software Artec Studio Professional 13 (Artec 3D, Luxemburg). This novel scanning routine allows archaeologists to perform more 3D-based studies on small lithic implements [ 58 ]. All 3D meshes analyzed in this paper are stored in an open-access repository available on Zenodo [ 75 ].…”

“…Lamentably, studies of 3D models have seldom focused on small-sized tools, which characterize most of the European Upper Paleolithic. The reason is primarily the technical limitations of surface scanners [ 58 ]. Although 2D geometric morphometrics studies, based on outline extraction from images, have proven to be effective in describing tool types with low variability in profile curvature [e.g., arrowheads: 59], the greater variability that distinguishes blade and bladelet blanks belonging to different phases of a core reduction sequence can only be successfully captured using the third dimension [ 60 ].…”

“…Particularly, we intend to identify specific designs of lithic artifacts that were proposedly aimed for by their makers [ 67 ]. The preliminary digitalization of artifacts was made possible by a newly developed protocol relying on micro-CT technology that enables researchers to scan hundreds of small lithic implements within a short period of time [ 58 , 68 ]. The obtained 3D meshes were then used to compute several quantitative variables linked to stone tool size and shape.…”

The Batch Artifact Scanning Protocol: A new method using computed tomography (CT) to rapidly create three-dimensional models of objects from large collections en masse

“…In some cases, multiple objects can be scanned simultaneously using medical or micro-CT. The output Digital Imaging and Communications in Medicine (DICOM) files are then interactively surfaced and then separated into individual files and cleaned using expensive, proprietary and GUI-based software such as Slicer, Aviso, or Geomagic (Göldner, Karakostis, & Falcucci, 2022). In these cases the scanning process is efficient but at the cost of an increase in post-processing time and, like the other methods, is not conducive for efficiently creating a full set of 3D models of objects from large collections.…”