Mostrare l’invisibile: il soffitto trecentesco nascosto del convento di Santa Caterina a Palermo

Digital surveying and representation technologies have been widely used for the visualization of works of art and architecture that no longer exist or have been moved from their original location. These researches share a common feature, that can be resumed by the motto “Display the invisible”, already used in research experiences [Colosi et al. 2015; Gambin et al. 2021]. The purpose of this research is the visualization of a 14th century wooden ceiling, painted by anonymous artists, that covered the hall used for the assembly of the Chapter in the convent of Santa Caterina, at the heart of the historic center of Palermo. The hall was reshaped at the end of the 18th century to serve as a sacristy: the longitudinal walls were covered by wooden wardrobes and a plaster vault, built above the wardrobes, concealed the painted ceiling. Laser scanning and photogrammetric surveying techniques have been used to build up a 3D textured model of the ceiling; this model has been used for two different visualization solutions: motion tracking for divulgation and remote fruition; Augmented Reality for on-site visualization. The experiment on AR visualization tested a tool for Unity, recently developed by Vuforia, that uses 3D scans of a real scene to calculate the pose and orientation of a mobile device. Both techniques mix the vision of the real scene with the visualization of the 3D model, thus “displaying the invisible”.