ARS3D African Red Slip Ware digital - 3D Documentation for the multi-perspective analysis of a central object genre of Late Antiquity

Finished
Scene from the Achilles cycle on the 3D model of an ARS shell. The motif of the centaur is highlighted for better viewing. Vanessa Liebler for the i3mainz, CC BY SA 4.0

The so-called African Red Slip Ware (ARS) is one of the most important for the understanding of Late Antiquity and its changes, as well as for ancient economic economic history of antiquity. The project, funded by the funded by the German Federal Ministry of Education and Research, deals with the is concerned with the digitization of the relief-decorated ARS of the Roman-Germanic Central Museum (RGZM).

Motivation

One of the most important aspects for the understanding of the late antique imagination and its for the economic history of this period is the so-called African Red Slip Ware (ARS). so-called African Red Slip Ware (ARS). The relief-decorated pottery was produced in large quantities in North Africa between the 3rd and 5th century A.D. and was and traded throughout the Mediterranean as far as Britain. The bowls, plates, jugs and pitchers are of outstanding importance. to them.

 With regard to their special medial qualities and the great knowledge potential for cultural-historical questions, the genre has hardly been studied, and has been insufficiently developed for corresponding analyses. One reason for this is the particular challenge of documenting the objects and their decoration. The representations applied to the vessels by means of relief appliqués cannot be precisely recorded with traditional 2D documentation methods due to the different curvatures of the vessels. In addition, the relevant literature lacks a standardized approach to the motifs.

The aim of the project is to open up a largely unpublished collection for research in an innovative and sustainable way by means of the precise 3D digitization of the relief-decorated ARS of the Roman-Germanic Central Museum (RGZM) and the construction of an ontology, thus not only enabling new research questions but also setting documentation standards.

Activities

The high-precision 3D data acquisition and processing of the ARS collection at the RGZM, about 325 objects, has been completed. It was performed with the projection scanner ATOS TripleScan from GOM in the laboratories of the i3mainz. of the i3mainz. To provide the 3D models with a realistic surface, the originals were the originals were scanned in the so-called “structure from motion” process from all sides with the system camera from all sides with the Nikon D800 system camera. After the processing, i.e., the generation of the 3D models and the subsequent the 3D-model and the photos are connected with each other, there is now for each textured 3D model for each object is now available for further analysis. available.

During the 3D capture and the subsequent processing steps, technical metadata is generated that provides the user with important information about the origin and quality of the data. A team from i3mainz and RGZM is currently working on a cross-project metadata schema to describe the technical process of creating the 3D models.

For the digital representation and processing of the textured 3D models, the open-source framework 3DHOP was chosen. Because of the high resolution of the objects and the associated file sizes, it is convenient to work with the NEXUS data format, which stores the original files in multiple resolutions. The viewer is automatically provided with the resolution that matches the current section. The 3D viewer is further developed using web technologies such as HTML5 and WebGL. A function that allows the user to interactively mark applikes in the 3D model has already been implemented. The scientific description and interpretation of the objects by the archaeologists will also be done in this step.

A geometric comparison process will help answer archaeological questions that depend on the degree of similarity between two appliques. First, the area of the applique to be compared is digitally cut out to determine its geometry. This is because during the manufacturing process, the geometry of the appliques was deformed differently by applying them to the respective vessel. The 3D model is transformed into a 2.5D representation by projection. After applying the projection, residual influences of the deformation are present, which are to be taken into account when evaluating the result in the archaeological similarity analysis. For further processing, the appliques are saved as 2.5D images.

For the geometric comparison of two appliques, approximate values for the deviations between the two 2.5D images are determined. Using an iterative image comparison procedure, the geometric relationship of the comparison candidates is determined. Based on this, colorized difference images and graphical representations of local displacements will be produced. These quantitative and qualitative results will aid archaeologists in their interpretations of possible similarities and consequently, for example, in assigning artifacts to workshops.

The archaeological observations and interpretations are compiled into a semantic structure called ARS3DOnto. The ontology provides the necessary framework to document meta-, para-, and provenance information of the recorded and processed 2.5D and 3D data from the African Red Slipware and its digitized and annotated applications. ARS3DOnto is modeled as much as possible on the concepts of CIDOC-CRM and the CRMDig or CRMSci extensions.  In addition to those of CIDOC-CRM, the ontology represents various axioms required to define ARS and its features. These axioms are related to the axioms defined by CRMs either by classes, subclasses or other relationships. The content semantically structured in this way is stored in an RDF triplestore.

Results

A virtual platform unites all 3D analysis and visualization tools as well as the semantic structure ARS3DOnto. It is already available within the project for processing the 3D models. In the future external users will also have the possibility to view the 3D models in the viewer and retrieve the results of the analyses.

For referencing and long-term archiving, the digital masters will also be made accessible via the object database Arachne of the German Archaeological Institute.