## 4 Method
### Model Generation and Information Mapping  
Nowadays, modelling software requires a high knowledge to generate 3D representations capable of communicating various information and numerical values. As briefly mentioned in the previous paragraphs, the creation of geometric elements corresponding to the architectural and structural components of a building allows users to share values such as area, volume, physical and mechanical properties of the materials. At the same time, 3D mapping techniques make it possible to effectively declare the materials used for the construction of the building and provide an appropriate basis for subsequent analyses such as material analysis, identification of historical phases and decay analysis. Thanks to this, it is possible to associate operations, restoration phases, construction sites, and scheduled maintenance at a later stage. The numerical values are associated with actions, moving from an informative 3D representation to a methodological approach capable of supporting the life cycle of the building through shared models, phases, databases, clouds, and many other forms of digital sharing. Consequently, creating a model must be the most faithful to reality, where the geometric values, the wall partitions and the constructive logic of the building correspond to the real building. For those reasons, the authors' research in recent years has addressed the paradigm of the complexity of heritage buildings and proposed methods capable of transforming simple points of origin from 3D survey to complex HBIM projects. On the other hand, given the growing need to tell a wider audience the tangible and intangible of our built heritage, new XR projects have been implemented, requiring specific requirements from the first model generation phase. Thanks to tests and analyses conducted in the digital representation of built heritage, it has been possible to define a sustainable workflow capable of exponentially reducing both the modelling and development phases of HBIM projects for XR environments. As anticipated in the previous paragraph, the modelling phase involved applying the grades of generation GOG9 and GOG 10 defined in an earlier study [3]. In particular, GOG 10 made it possible to automatically transform complex geometric models from 3D surveys into HBIM objects capable of receiving and sharing different types of information. The application of GOG 10 for the Church of San Valentino envisaged, at the basis of the process, the use of the point cloud and the textured mesh model from both terrestrial and aerial photogrammetry. The development of the model involved the following phases:  
* Import of point clouds and textured models from digital photogrammetry into NURBS modelling software;
* Integrated application of GOG 9 and GOG 10 for the generation of complex and unique elements such as the complex vaulted system of the church, out-of-plumb walls, structural elements, roof and bell tower;
* Automatic transformation of complex NURBS elements into HBIM objects for the creation and sharing of a BIM project, schedules, two-dimensional drawings;
* Information mapping: insertion of information for each HBIM element created to expand the digital model's information value. The model generation phase saw the integrated application of GOG 9 and 10 for the generation of the vaulted system of the Church of San Valentino. Despite being a small building, the church has unique elements of its kind, which required a digitisation process to go beyond the traditional modelling techniques found in BIM software such as Autodesk Revit and Graphisoft Archicad. In particular, the church has two rib vault systems. Rib vaults permitted the construction of much thinner and higher walls and stained glass windows of enormous size, which flooded the cathedrals with light. The rib vault improved upon the earlier Barrel vault, with semicircular arches, widely used by the Romans.