## 3 Results
### Three-Dimensional Modeling
#### 3.1.1 Surface Modeling  
The treatment of the captured information was targeted at modeling by means of a set of vector graphic entities (CAD planes or NURBs) of the _shell_ that surrounds the material volume of the object studied. For this purpose, which relies on software specialized in reverse engineering, in this work the version 2016.1.0. of Geomagic Design X (3D Systems, Inc.) was used.  
In that software three differentiated processes were developed:  
* Conversion of the point cloud into an optimized triangle mesh. This process is performed automatically by the software based on the definition of a series of parameters related to the overall size of the mesh and the increase or decrease in density in those areas where the shape of the object so allows, in order to optimize the result (Figure 3).
* Segmentation of the meshed surface. Automatic process that, depending on variables related to accuracy parameters, consists of the subdivision of the mesh into regions of recognizable basic geometry (planes, spherical surfaces, conical surfaces, etc.) or generic (NURBs) (Figure 4).
* Manual conversion of regions into CAD surfaces and their edition by means of manual modification tools to formalize the joints (Figure 5).  
This last step is crucial when establishing the level of accuracy or fidelity of the final model with respect to the physical reality of the object treated. This aspect can be controlled by consulting the deviations produced between the mesh and the resulting CAD model (Figure 6).  
Figure 4: Partial view of mesh segmentation in regions of recognizable geometries. The low quality of the mesh in areas of high formal complexity (such as decorative elements) due to the difficulties mentioned in the survey process, have produced an excess of regions. This circumstance has not prevented the implementation of the proposed modeling method for the surfaces that define the general shape of the facade.  
Figure 5: Exterior and interior views of the CAD model once edited.  
Figure 3: Partial view of the mesh surface obtained from photogrammetric point cloud. Mesh size: 1,771,241 triangles.  
The data collection used for photogrammetric capture was somewhat rugged because there was still activity in restoration works, so that there was areas of very poor quality in the final point cloud. This circumstance did not prevent executing the process described successfully for most of the object, extrapolating well-defined geometries to those areas (quite small compared to the total) lacking sufficient information. Since it was a pilot experience, the principal aim was to verify the proper functioning of the method proposed in general, rather to obtain rigorous results for the whole three-dimensional model.  
On the other hand, the reverse engineering software used is capable of generating complex NURB surfaces adapted to the mesh in regions bounded by the user, making it possible to include figurative elements in the surface model of the object (in this way the decorative medallions of the panels were developed). In any case, since the generation of these types of surfaces required more extensive processing times, it was necessary to make decisions regarding the formal complexity of the resulting object to optimize the times and resources. In that sense, it was decided to make geometric simplifications of certain elements, such as the capitals of the pilasters, the decorative elements of the frieze or the figurative elements of the window that illuminates the _Sacrista de los Calices_.