## 4 Derived Products and Data Processing
### Dem  
The first approach to the problem: a solution based solely on Agisoft allowed us to discover the suitability of the method used to obtain the 3D model. For the first time, we were able to observe the engraving grooves in detail from a DEM hillshade. This technique generates a raster image where each pixel is assigned an illumination value that depends on the location of a hypothetical light source. It, therefore, requires four input parameters: azimuth and elevation angle of the light source, slope, and exposure [25]. The result is an indexed or grayscale image that reflects direct shadows and light. In this case, the program allows you to select the following parameters (Tools/Preferences/Appearance/Ortho) as well as the color palette and the position of the light source (Azimuth and Elevation). Three different hillshades were exported (Figure 6) varying the azimuth angle by 60\({}^{\circ}\) and using grazing light (with an elevation angle of 30\({}^{\circ}\)). The images can be imported into a CAD, into a GIS, or directly stacked in a single Photoshop file (layers).  
Observing the different images in Figure 6, we see that hillshading offers a similar result to that obtained with the RTI technique. The lines of the engraving become more or less visible depending on the lighting angle of incidence. Ideally, the light should strike perpendicular to the lines. Three hillshades have been exported but as many synthetic images can be obtained with a simple and quick modification of the light source in Agisoft PhotoScan Professional. Although this solution presents the RTI technique  
Figure 6: Hillshades detail exported by Agisoft PhotoScan. In each image the position of the light source is different. It moves 60\({}^{\circ}\) azimuthally, while the elevation remains constant at 30\({}^{\circ}\): (**a**) azimuth = 75\({}^{\circ}\); (**b**) azimuth = 135\({}^{\circ}\); (**c**) azimuth = 195\({}^{\circ}\).  
virtues, it suffers from its defects when it comes to extracting the final layout of the figure. According to [PERSON] et al. [6] the use of artificial grazing light increases the subjectivity of the perceived motif, since depending on the angle, power, and light source direction, some areas are enhanced to the detriment of others, sometimes generating shapes that can be misleading. The proposed solution was to export a significant number of hillshades so that all the traces were clearly visible and then delineated on the different images to obtain the tracing. Using, as other researchers do when presenting the final tracing, GIS [8] or more professional graphic design programs such as Adobe Illustrator [5; 11; 14] or Corel Draw [26]. However, it was decided not to use this solution. Looking for an alternative that dispensed with shaders, where the lines of the engraving were automatically extracted in order to minimize operator intervention (subjectivity).  
For the rest of the analysis, the program HyperCube v. 11.5 was used. It is a program specifically aimed at the visualization and analysis of multi and hyperspectral images. In addition, it allows filtering, warping, mosaic creation, resampling functions, and the ability to perform arithmetic operations on images and data. This program has been used by other rock art specialists for purposes and uses other than ours [12; 27; 28]. There are several operations performed with HyperCube using as a base the DEM in 32-bit TIF format exported by Agisoft. The following sections detail the tools used and the objectives achieved.