Scan-to-BIM Process Versus 3D Procedural Modelling of Gothic Masonry Vaults

Abstract

The so-called “Scan to BIM” process has been widely utilized for many years now: deriving 3D models from point clouds often a local modelling of geometric components is necessary. This leads in most cases to use external modelling tools and or complex local modelling processes involving often procedures quite time-consuming. The paper describes a workflow aimed at the 3D procedural modelling of a quadripartite rib vault system. Starting from feature extraction of TLS data based on geometric assets, we provide a workflow to turn TLS point clouds into the geometric primitives of the complex vaulted systems covering the main body of the church of Nostra Signora della Speranza in Cagliari (Italy). Vaulted systems are architectural valuable elements characterized by a fairly large and varied number of case studies; today, also thanks to the use of TLS systems which we now have available, we can consider the geometric structure with a precision previously, until not long ago, unreachable. The geometrical information of the scanned element is the basis of a procedural modelling that aims at writing an algorithm for the parametrization of the modelling process of the different surface elements of the vaulted systems. The proposed methodology lends itself to an effective application in the BIM environment, in particular in those cases where recourse to local modelling is necessary. Thanks to the parametrization of the process, we can overcome some of the limitations of local modelling, often in contradiction with the BIM philosophy itself, which requires the use of flexible and reusable parametric models.