Historical military heritage: 3D digitisation of the Nasri sword attributed to Ali Atar

Abstract

Ali Atar, Warden of Loja and Lord of Zagra, was born around 1393. He was one of the principal military leaders of the Nasrid period and came to join the Grenadine Royal House by marrying his daughter Moraima with Boabdil, the last King of Granada. He died in the battle of Lucena in 1483, where one of the magnificent jineta swords of Andalusí manufacture was snatched, which is now conserved and located in the collection of the Toledo Army Museum (MUSEJE). The MUSEJE collections house important scientific, technical, historical and artistic heritage. The historical military heritage needs for its protection, preservation and valorisation the adaptation of new resources and benefit from the usage of new digital technologies. The physical conservation is no longer enough for a resource as valuable as cultural heritage; it needs to be complemented with a comprehensive digital preservation in all its forms, being essential and necessary for its proper safeguard. The virtual era currently emphasizes its presence in the digital documentation, preservation and dissemination of our cultural heritage. In particular, we have oriented and activated it on the historical military heritage, knowledgeable and narrator of our history, of its treasures, and of their relationship within the society as important representations of social and dynastic status. This paper is centred in the 3D digitisation by means of digital photogrammetry and 3D modelling of a historical military weapon. Aided by photogrammetry and information and communication technologies (ICT), we will achieve precise geometric documentation and 3D models that are geared towards research, education, diffusion and the preservation of heritage as important and unknown as is historical military heritage. Photogrammetry gives us the opportunity to bring to light the Ali Atar’s sword, one of the most relevant artistic manifestations belonging to the Nasri armament (Fig. 1, Table 1). The multi-view close-range photogrammetry is key to virtualise this jewel and also to contribute to the democratisation of the museum through the web dissemination of its content in a personalized way.

Materials such as metals and precious stones, and gold techniques present in the Andalusian weapon required a particular photogrammetric data acquisition using a light booth and polarizing filter (Fig. 10), as suggested for the latter by (Guidi, Gonizzi, & Micoli, 2014). This setup brought a substantial improvement when dealing with highly reflective materials such as the metallic blade of Ali Atar's jineta sword. The use of the polarising filter attenuated the light that affects and reflects in the piece, benefiting both data acquisition and processing to deliver 3D models. We offered some results ready to safeguard, preserve and disseminate the jineta sword as a high-quality 3D model (Fig. 13), with submillimetre precision from which to obtain all the necessary metric deliverables. From the dense point cloud, two meshes were delivered: i) a homogeneous high resolution mesh keeping all the original features for archiving, conservation and research, and ii) a medium resolution mesh for web-based visualisation and dissemination. The aim was to achieve a detailed geometric documentation as well as complete and accurate 3D models (Fig. 29) for web repositories (https://skfb.ly/ZzzA), orthoimages (Figs. 30 and 31) that allow us to plot from CAD programs all the ornamental and decorative information of the piece (Figs. 32 and 33). In addition, we present some results related to monitoring and evaluation of changes in the state of conservation of the piece (Figs. 34, 35 and 36), extending the survey to preventive conservation studies.

This research proves the value of geometric documentation techniques for the democratisation of museums. It contributes to improving the research processes, opening a new line of study. From this point we can rebuild the past through the virtuality, being able to mark and confirm historical hypotheses. These techniques offer the chance to give value to relevant and singular pieces in and out of museums. Both heritage and virtual archaeology are fundamental pillars to delve into the future of education and knowledge.