Tecniche innovative per il rilievo, la rappresentazione e la fruizione dei beni culturali. Il soffitto della Sala Magna di Palazzo Steri a Palermo

This work is focused on procedures and methods for the production of photorealistic and geometrically correct 3D digital models. The investigation has been addressed to the wooden painted ceiling of the “Sala Magna” in the “Palazzo Steri” of Palermo. The building of the “Steri” starts in 1320 on behalf of Manfredi I Chiaramonte and continues with his heirs Manfredi II and Manfredi III, who built the second floor and provided the building with decorations. In 1601 the Holy Inquisition moved to the Steri and transformed it in a place of imprisonment and torture. The hall in the northern side of the first floor, named “Sala Magna”, was the main room of the building. The ceiling of the “Sala Magna” is made of 24 wooden beams enriched with paintings of saints, barons and tales from the Holy Bible, according to a spread habit in the sicilian culture of the time. This research work has been developed through three steps: data collection, modelling process and texture mapping. Data collection has been performed with topographic, photogrammetric and laser scanning techniques. Two different devices have been used in laser scanning survey: Mensi GS 200 and Faro LS880. A huge point cloud of 15 million points has been used to produce a triangulated surface model of the ceiling. Topographic and photogrammetric survey have been addressed to the production of rectified images of the planar faces of the wooden beams. Modelling process has been performed using planar curves, automatically extracted from the triangulated surface; a CAD model of the entire ceiling has been produced. The CAD model has finally been textured using the rectified images, in order to produce a photorealistic and geometrically correct 3D digital model. Such model can be used both for navigation and geometric inspection.