The recomposition of fragmented objects: the case study of St. Andrea statue at Stiffe, L’Aquila

The work that we present refers to procedures of 3D survey and automated processes of virtual re-composition and re-position of fragmented objects. The case study is the restoration of a 15th–century painted terracotta artifact, the statue of Saint Andrew, from a church in Stiffe, a small village nearby L’Aquila in Italy. This beautiful statue was severely damaged during the 2009 earthquake when it fell to the ground and fragmented into 80 pieces 0.5-80 cm in size. Conservation treatment started in 2012 and was concluded in summer 2014. The goal is to describe the restoration process about reassembling fragmented artwork with the adoption of 3D survey and modeling procedures. We present some original procedures for sculpture reassembling using high accuracy instruments: acquisition of metric data through laser scanning and/or photogrammetry, 3D modeling of separate fragments, cloud segmentation using parallel sections, point color and reflectance to detect external and internal surfaces, fracture or contact regions with other fragments, contour extraction, internal volume definition. The indications of digital reconstruction actually reduced the manual checking of matched pairs, being the fragments too fragile or heavy for safe and direct manipulation and allowed the restorers to reassemble a chaotic puzzle composed by a large number of pieces avoiding loop mistakes.