## 5 Methodology
### 3D Reconstruction of Architectural Features  
Using the work of the research team's engineers, surveyors, and conservator-restorers, a 3D model was constructed containing the building's architectural structures and features. In this model the church was restored to its original appearance prior to the fire [49; 52].  
This stage commenced with a topographic survey performed using the Leica TCRP1205 Plus R400 Total Station. This survey was used to establish the floor plan of the church, the height and position  
Figure 2: Workflow combining topographical survey, terrestrial photogrammetry and analysis, and the processing of digital images for rendering building reconstructions in 3D.  
of the pillars, and the height of the walls. Data was also gathered from the arches that still remained standing in order to calculate the true shape of their curves and to record their dimensions. In the area of the altar and the presbytery, measurements were taken for the visible pictorial elements on the walls using a tape measure, and then cross-referenced against the points measured on the planimetric map. This was done so that the building's planimetric map (Figure 3) could be used to provide references during the digital reintegration of the mural paintings.  
The church has a rectangular footprint with two visible facades. The convert building adjoins the other two facades. A photogrammetric survey was performed for both facades using 50% overlap. Metashape 2019 (a new version of PhotoScan) was used to do the analysis, image processing and facade restitution, obtaining their orthographic representation (see Figure 4).  
The floor plan was produced using AutoCAD and the surveyor data. The work by [PERSON] [53] was then used to create a 3D model of the architectural structures of the church. Using the aforementioned floor plan and height measurements as the starting point, the 3D modelling process began with the inner walls and floors of the church. Once complete, the modelling process continued with the pillars and the archways that divide the interior space (see Figure 5). Next, architectural features were added, and the surveys of the church's two visible facades were incorporated, giving them volume. This entire process culminated in the creation of the coffered ceilings and small ornamental elements, i.e., doorframes of wooden doors, roofs and ceilings, pillar decorations, and the vault crowning the side door. All of these elements were recreated using antique photographs and onsite visual inspections of existing remains, irrespective of their state of deterioration.  
Having completed the detailed 3D modelling of the church, the research team then proceeded to add texture to the model in order to create a realistic appearance. The texturizing process consisted of adding colours and material textures (wood, stone, metal, etc.) to the model. For some elements, these textures were recreated using onsite photographs taken of the pillars, walls, arches and wooden doors; however, for others, such as the paved floors, researchers searched for and edited images of a similar appearance in order to obtain results as faithful to the original as possible. Finally, researchers incorporated the digitally retrieved images of the altar and presbytery frescos (see Figure 6) into the 3D model. The process through which these digital images were rendered is described in detail in the following section.  
Figure 4: Scale drawings of the main and lateral facade obtained using photogrammetric restitution.  
Figure 5: Detailed three dimensional (3D) models: (**a**) building and architectural structures, (**b**) pillar.  
Source: Cor-Ignis Project.