EUROGRAPHICS Workshop on Graphics and Cultural Heritage (2020) F.-J. Melero and M. Spagnuolo (Editors) Interaction with 3D models on virtual archaeological sites L. Ortega 1 , Á.L. García-Fernández 1 , J.L. López 1 and A. Calzado 1 1 Computer Science Department. University of Jaén, Spain lidia@ujaen.es, algarcia@ujaen.es, llopez@ujaen.es, acm00174@red.ujaen.es Abstract The extraction of artifacts during the excavation of an archaeological site usually implies the loss of spatial references among the extracted vestiges. In this work we introduce a way to compute spatial relationships among the finds in an excavation, as well as a method for accessing the information on the database through the virtual 3D representation of an archaeological site. The spatial relationships are encoded in the database using the Dimensionally Extended Nine-Intersection Model (DE-9IM). CCS Concepts • Information systems → Spatial-temporal systems; • Human-centered computing → Graphical user interfaces; Information visualization; 1. Introduction and main contribution Nowadays, archaeological procedures and methodologies are grounded on many disciplines, highlighting among them the ICT (Information and Communication Technology). Archaeological documentation has benefited from database systems, normally con- taining heterogeneous data sets. However, traditional databases present a lack of cohesion or link among data fields that hinders the processes of querying and subsequent analysis of the data. An ex- ample of this disaggregation is the set of photographs that comple- ment the information of the text fields in a record. By themselves, images do not facilitate automatic analysis. As a result, data items of different nature are not integrated; they should be displayed with different visualization tools and thus have to be analyzed indepen- dently by an expert. Keeping information about the status of the archaeological sites before excavation is crucial for future analysis. Once an artifact is extracted from the site, its spatial reference is definitely lost un- der the premise: "excavation is destruction" [Luc11]. Most of the efforts in the extraction process are aimed at gathering as much in- formation as possible, in order to facilitate further analysis. Record- ing systems normally include positioning information, images and an exhaustive description of the find, however stored as individual items. In fact, spatial relationships with the rest of the surrounding artifacts should be considered by means of spatial databases incor- porating topological relationships [Ege93]. In this way it would be guaranteed that once an artifact is extracted, it is linked to its envi- ronment for posterity, just as it was in the past throughout centuries or millennia. Topological operators have already been studied in archaeol- ogy [BM17]. The topological model named "Dimensionally Ex- tended nine-Intersection Model" (DE-9IM) is defined as a 3x3 ma- trix which determines the spatial relationships between two 2D ge- ometries [CSE94]. This matrix can be extended to 3D by defining the same concept in a more complex 5x5 matrix or 25-intersection model [ZG19]. Although associating relational operators to each pair of spatially related artifacts can be enriching, it does not replace the expressiveness that a real visualization can provide. Therefore, the records must be completed with figurative elements such as images or photographs. Again, the result is still a hetero- geneous and decoupled dataset. Therefore, 2D images should be replaced by the 3D models of the artifacts. 3D scanning of the finds, especially of those pieces considered singular or important, is a major desire of many archaeologists. Even though it is not al- ways feasible to obtain 3D models of all artifacts, the possibility of recreating models in digital format while keeping their scale, shape and appearance, allows to overcome most of the disadvantages dis- cussed above [RCM * 15]. Among them, we highlight the virtual recreation of site conditions in terms of visualization, interaction, and even collaborative analysis through a web portal [GCD * 16]. In our framework, spatial relationships can be incorporated to complement the aspects described above. Our approach is focused on an integrated system with high resolution visualization which is able to show the models of the finds distributed in the same spatial arrangement as in the archaeological site. Interaction ben- efits from 3D visualization, as it is already known as the most in- tuitive way to access information [BIF04]. Clicking on a model can initiate a set of different operations, including spatial and non- spatial analysis. This approach includes connections among the finds recorded in the database as they are found during the exca- vation. While real artifacts are extracted, their spatial arrangement can be recorded by means of some technique, for example by pho- c  2020 The Author(s) Eurographics Proceedings c  2020 The Eurographics Association. Short Paper DOI: 10.2312/gch.20201286 https://diglib.eg.org https://www.eg.org