A Hybrid Model for the Reverse Engineering of the Milan Cathedral. Challenges and Lesson Learnt

Abstract

Cultural Heritage (CH) 3D digitisation is getting increasing attention and importance. Advanced survey techniques provide as output a 3D point cloud, wholly and accurately describing even the most complex architectural geometry with a priori established accuracy. These 3D point models are generally used as the base for the realisation of 2D technical drawings and 3D advanced representations. During the last 12 years, the 3DSurveyGroup (3DSG, Politecnico di Milano) conduced an omni-comprehensive, multi-technique survey, obtaining the full point cloud of Milan Cathedral, from which were produced the 2D technical drawings and the 3D model of the Main Spire used by the Veneranda Fabbrica del Duomo di Milano (VF) to plan its periodic maintenance and inspection activities on the Cathedral. Using the survey product directly to plan VF activities would help to skip a long-lasting, uneconomical and manual process of 2D and 3D technical elaboration extraction. In order to do so, the unstructured point cloud data must be enriched with semantics, providing a hierarchical structure that can communicate with a powerful, flexible information system able to effectively manage both point clouds and 3D geometries as hybrid models. For this purpose, the point cloud was segmented using a machine-learning algorithm with multi-level multi-resolution (MLMR) approach in order to obtain a manageable, reliable and repeatable dataset. This reverse engineering process allowed to identify directly on the point cloud the main architectonic elements that are then re-organised in a logical structure inserted inside the informative system built inside the 3DExperience environment, developed by Dassault Systémes.

Towards Master Data Management for Cultural Heritage: The Sacri Monti Web Platform

“…On the other side, commercial components usually ensure longer-term support and more stability, but this comes at a higher price. The modelling phase is undoubtedly time-consuming if carried out with manual methods, a reality-based approach, and high accuracy (Acosta et al, 2022;Spettu et al, 2021). A possible solution is using the point clouds as the geometrical basis.…”

Web Platforms for Cultural Heritage Management: The Parco Archeologico Del Colosseo Case Study

“…It has to be considered that several services require a subscription which amount varies according to the selected features and the available storage. Another significant advantage is represented by the enhanced possibility of sharing up-to-date information and data between users, with a significant reduction in terms of data duplication and version proliferation (Achille et al, 2019;Fassi et al, 2017;Spettu et al, 2021). As the access to the platform is made through a web browser and that can be made potentially from any digital device, the rendering of the viewer interface usually adapts to the computational capabilities of the device.…”