Optical sensing technologies for the generation of reality-based 3D models of Cultural Heritage artifacts

The central theme of the thesis is the use of triangulation laser scanning and other optical three-dimensional surveying systems for the realization of 3D models of objects of historical and artistic interest - sculptures, archaeological finds, decorative elements in architecture. The subject is faced keeping in mind the purposes and needs the models should or could meet, and which are the challenging steps to become a more common tool. To name one, a fundamental aspect is bridging gaps between technology providers and Cultural Heritage practitioners. Research for new functional applications is directed, for instance, towards the development of models as visual reference bases for data of various provenance, or as part of more effective, interactional and/or immersive outreach programs. Technologies and procedures for data acquisition and processing are extensively analyzed both under a general view of the state of the art and of national and international authoritative undertakings, and within the scopes of two hands-on applications, planned and carried out during the PhD course, for documentation and communication in archaeological and art-curatorial panoramas: - The MUSINT project, which has reunited in a Web-based interactive exploration system several Aegean and Cypriot collections held by Tuscan archaeological museums, and has a strong point in the possibility of viewing a high number of 3D models; the other outcome is the prospect for specialists to examine off-line the high-resolution versions. - The Martelli project, which is aimed to support the visit to a distinguished Florentine house-museum and its art-collection with personalized multimedia itineraries and 3D engagement (with also a solid model), reconnecting threads between art-works belonged to the noble family and sources of historical evidence, and between both of them and real spaces. The projects described are presented after giving a detailed review of relevant and still open matters in the specific field of application, either practical or theoretical ones: orientation through suggested best practices and shared guidelines, definition of standards and validation procedures, sharing in / access to centralized archives of 3D data, archiving file formats and media, and so on. The case-studies have given the opportunity to apply referential principles and share an optimized methodology to create 3D content in similar projects, taking in account a great variety of objects and divergent interests. The many 3D models created for the above-mentioned projects are evaluated considering various criteria highlighted while going in-depth in the concept of “quality” (a few even diametrically different), as: the measurement performance of the surveying systems in relation to different shape features, sizes, materials, set conditions; the apparent trueness resulting from mesh and texture processing operations and from final adaptation in the visualization system; the level of information transparency given to the end-user through appropriate metadata; the long-term usability of data archived at intermediate stages; the easiness of use; the degree of interaction allowed by the final infrastructure, etc. These factors can change and, in different combinations, influence the assessment, depending on the end-user of the system the models are included in. Yet, quality can be consistently read as the extent to which models actually represent and convey what they claim to. Basically, a high-quality 3D model should improve the capability to study and work on an object for art-historical research and conservation purposes and also to communicate better all the information that a direct view can’t transmit, enhancing the user’s experience and participation. As all high-tech solutions, 3D model and interactive environments are to be preferred only to the extent they are efficient in conveying content, and not in themselves.