Hypogea of San Pietro in Vincoli at Sant' Angelo in grotte

Since many years the research unit of the Sapienza University of Rome has dealt with the cataloging and surveying of several examples of rupestrian architectures in Italy and Cappadocia. In 2017 hypogea of the nineteenth-century church of San Pietro in Vincoli in the village of Sant'Angelo in Grotte (Italy) have been surveyed. For the first time in 1954, during pavement removal work were discovered hidden and forgotten cavities. A small chapel with a rectangular plan covered by a barrel vault was found. The surfaces of the chapel were completely painted with representation of the spiritual works of mercy, the Celeste Jerusalem and the Sun. The paintings were stylistically attributed to the Sienese school and placed temporally atthe end of the XIVth century. In another room a pictorial trace remained near the area of the vault. Unfortunately the vault and the entire pictorial cycle have been completely lost, probably due to the intense earthquakes in 1456 and 1805 that have tragically marke(i the life of this village. Between the two seismic events, probably took place the "covering" of the ruins and the construction of a new place of worship for the community. After 1883 the archpriest Federico Taddei rebuilt the main church as it is now. A phase-based laser scanner was used for surveying the entire hypogea systems. The scans were performed completely in the dark for registering the morphological data and favouring an homogeneous acquisition of the painted surfaces through the reflectance information. With a high definition reflex camera, a fixed optic lens and a color checker several images of the main chapel were taken in order to control the chromatic appearance of the paintings and the homogeneity of the lighting sources. The entire numerical model was processed with different procedures. The surface reconstruction was performed with algorithms able to reduce the points, maintaining however a good quality of the morphology. In particular the mesh model of the chapel was mapped with the high resolution images. Some specific tools were applied for the texture mapping of the vault. The result has been a navigable 3D virtual model with realistic images. Further elaborations were performed for the canonic representation of plans and sections through the method of the "contour lines". Experimented in different projects in Italy and Cappadocia the method allows to exploit the classic representation method and the use of multiple sections for the shape analysis of the rupestrian architecture. A detailed study concerned the surfaces of the chapel that belong mainly to planar and striped surfaces. The surfaces have ben unrolled for observing the paintings in the real shapes out of the morphological context.