Il «Fregio dell’arte della guerra» a Urbino: tra ricostruzione virtuale e rigore scientifico

The wing façade extending along the north and east elevations of the Ducal Palace of Urbino was characterised, until two and a half centuries ago, by the presence of seventy-two limestone bas-reliefs constituting the so-called 'Frieze of the Art of War'. Placed along the espalier of the Palazzo's outer seat, the frieze was exposed to the elements for about three centuries before being dismantled and placed inside the Soprallogge in the mid-eighteenth century, undergoing continuous relocation to various rooms of the palazzo from the 1940s-50s. The question of the original sequence of the bas-reliefs on the façade has not yet been fully clarified, despite the various testimonies over the centuries. The present work was created with the aim of documenting and reconstructing the original sequence of the bas-reliefs, starting from historical and iconographic sources, but above all from a careful analysis of the state of conservation and the different types of degradation to which the bas-reliefs have been subjected, as well as from observations on the variations in patina tone, which would be a valid tool for identifying possible correlations with atmospheric parameters (sunlight, temperature, precipitation).A prerequisite of conservation is respect not only for the work of art, but also for the historical datum closely linked to it, therefore considering the building in its diachronic evolution, through the reading and recognition of the building in its complexity. The project has therefore carried great responsibility and has been managed in a balanced, scientific and correct manner using all the knowledge tools, from historical analysis to the metric survey, from topography, from the study of materials to their origin to the factories that produced them and the problems of degradation related to them, in a combination of professionalism and competence.The first level of knowledge was, of course, metric, and therefore the aim was to quantify the data of the architecture in a given space to which the detailed surveys of each bas-relief could be correlated. The research project was divided into two phases: one of acquiring quantitative information through the geometric-formal surveys and one of a qualitative nature through the processing of the models. From this point of view, proposing, through a series of interventions, the survey and representation of a building, both from a methodological and instrumental point of view, means bringing back to the forefront an activity that involves various operators today and that must in any case find common ways of interpretation through unequivocal codes, symbols and graphic signs. In this overall research activity, the survey therefore appears as an "open system of knowledge" from the detail of individual elements to the complex of the analysed organism in constant relation with the environmental context. The second part of the work saw, as part of a project involving the reproduction of the bas-reliefs and their subsequent original relocation, the comparison of different surveying methodologies in order to verify their economy (time and cost), accuracy, limits and reliability. The tests carried out on a number of bas-reliefs started from geometric-formal surveys of the classical type, which formed the basis of comparison for the subsequent three-dimensional surveys illustrated below: laser scanner surveys; photogrammetric surveys and processing with Image Master Pro software; photographic surveys and processing with the open source software Phyton Photogrammetry Toolbox and Meshlab and with the ARC3D web service. The different surveying techniques are illustrated with the objective of achieving a correct as well as metrically exact representation of the asset considered, emphasising the problem of the quality and verifiability of the data surveyed both in terms of the reading and interpretation of the object, and in terms of measurement, and finally in terms of representation. The work presented was developed in two different moments, the first dating back to the 2007-2008 academic year, when with the students of the three-year course of Technologies for the Conservation and Restoration of Cultural Heritage within the teaching of Topography we carried out an exercise on the subject of surveying. The second moment dates back to the academic year 2013-2014 when the research on the hypotheses of recomposition and techniques for reconstructing the tile was presented at the Trento Conference at the International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 3D-ARCH 2013 - 3D Virtual Reconstruction and Visualization of Complex Architectures, which was awarded the prize for the best paper for scientific content and originality of the topic.