## 3 Results
### An Example: AR Application of the Archaeological Site \"La Matilla\"
Therefore, it is to be expected that there will always be backup for maintenance of the application so that it is always available to visitors (point 8 of the decalogue). To develop the proof of concept we have so far, we followed the procedure shown in Figure 6.  
The 3D digitization process consisted of the combination of three different technologies: laser scanning, structured light scanning, and digital photography. Since each of them produces data with different resolutions, we decided the following strategy to concurrently apply them in the way that was fastest and most optimal:  
* The laser scanner was employed to digitize the exterior area of the site, producing 3D high resolution coloured point clouds. * The structured light (handheld) scanner was used to acquire the interior of the three ovens, producing 3D high resolution textured meshes. * The digital camera was utilized to take hundreds of photos of both the exterior area of the site and the interior of the ovens, for later use in photogrammetry software. After the computation, 3D low resolution textured meshes were generated. Then, the next stage in the procedure is the processing of all the data obtained separately from each capturing technology to generate the 3D model of the site. We can summarize this step by enumerating and briefly describing the sequence of tasks that compose this process:  
1. Filter: eliminate undesired data and errors. 2. Register: apply the appropriate transformations (position, rotation, scale) to make all the sets of 3D data accurately fit to one another. 3. Fusion: generate a unique mesh with all the information provided by the digitization technologies. 4. Repair: analyse and correct the errors of the mesh to generate a manifold mesh. 5. Texture: compose a unique texture map with optimized distribution from all the texture information generated by the different digitization technologies used. At this point, we have a digital, accurate 3D model, useful in a great variety of applications. Regarding the application of AR, since it is intended to run on mobile devices,  
Figure 6: Scheme of the procedure to produce the proof of concept of the AR application. both the resolution of the 3D mesh and the texture must be reduced. This leads to a third stage in our procedure: 3D data adaptation. It consists of the following tasks that provide the results shortly described below:  
1. Decimate: drastically reduce the number of points of the mesh. 2. Optimize: slight reduction of the number of points optimizing their distribution, concentrating the points where curvature is greater. 3. Divide: split the mesh into smaller parts to be visualized in different scenes of the AR application. The reason for doing this is due to the technological limitations of mobile devices when representing big 3D objects. This task is related to both the decimation and optimization performed in the previous tasks. 4. Texture optimization: To alleviate the processing of 3D data visualization in mobile devices it is also important to compose the texture map in the most optimal way. After this stage, the 3D data are prepared to be integrated in the AR application. Finally, the application itself is implemented. A simple way to explain its development process is by dividing it into the following tasks:  
1. Design partial scenes of the archaeological site. In our case, we had five 3D-optimized models as a result of the previous stage: two corresponding to the external area and three corresponding to each of the ovens. These models are now enhanced by adding ornamental 3D models or by including background sounds, resulting into five different scenes. 2. Generate interfaces and explanatory texts. It is important to design a usable application that provides the adequate material to help people improve their knowledge, learn, and enjoy, and that generates the need for further information about the site. Interfaces must be intuitive since it will be used by a very diverse group of people (points 8 and 9 of the decalogue). 3. Assign 2D markers.