Stephan KARL | Paul BAYER | Hubert MARA | András MÁRTON
(Independent, Graz, Austria)
Keywords: Computed tomography, Texture mapping, Corinthian pottery, Vase painting, Feature vectors
Abstract:
Profile-drawings and tracings are essential elements of a throughout scientific object documentation in archaeological pottery studies. Within the study of Greek pottery, unwrappings of painted surfaces have a long tradition and a still well-deserved high significance. They show the depiction without photographic distortions or sectioning, enabling archaeologists to analyse and interpret the image as a whole. This is especially true in the case of Corinthian pottery, where the poor preservation of the painting tending to flake off often results in unclear photographs. Nevertheless, traces of flaked off painting layers are still visible on the surface under specific illumination.
Creating profile-drawings and unwrappings manually is time-consuming. Manual acquisition with tactile tools like lead wires, profile combs or tracing paper is often not allowed due to the fragile nature of the surfaces. To facilitate this task for pottery archaeologists, we propose a combination of 3D data derived by photogrammetry (SfM) and computed tomography (CT), where each technique can also be on its own. The fusion of different data sources is a new approach. It exploits the specific strengths of these not-contact digitisation technologies: SfM with a high resolution in texture and CT with a high accuracy in geometry as well as with the added value of providing inner surfaces of closed vessels.
Having SfM and CT data, we can combine them by transferring colour information to the vertices of the CT model. Afterwards, we use the GigaMesh Software Framework for enhancing geometric features in the surface data, in our case the fine incisions of the black-figure style. Doing this, we are able to create accurate and sufficiently detailed unwrappings aligned to the needs of pottery specialists. Additionally, we can compute profile lines with inner and outer contours and unwrappings of the inner surface showing significant details of the manufacturing process.