*2.1. Pre-Production Stage*

The pre-production phase of the pipeline had to ensure that the restrictions that were imposed on the shooting inside the tower were not insurmountable, since the rest of the lines of work could be readily controlled. After a process of documentation and deliberation about the different possibilities, it was concluded that the only certain method of covering the surfaces in such a short time and without lighting aids was to use a vertical rig of cameras shooting simultaneously (See Figure 2). The preparation of each shot would take more time, but if properly synchronized, the total time required could be divided by the number of cameras used. Initially, calculations were made for a vertical rig consisting of four mid-range DSLR cameras anchored to a rigid, telescoping pole on a tripod. The path of the rig would be parallel to the walls in different passes at different distances, and the relative position of the cameras on the rig would be changed to obtain segments at different heights. According to the specialist literature, this approach has rarely been used for photogrammetry projects and it is much more common to find stereoscopic approaches using two cameras [3,32].

The cameras that were used were four Canon EOS 1200D with 25–80 mm lenses for the main room, and one additional Canon EOS 60D with a 24–70 mm lens for the second room, bringing the total to five simultaneous cameras. The cameras were set to a resolution of 5184 × 3456 pixels, about 18 MP (megapixels). The sensor of both rooms was identical, and according to the manufacturer had a total of 18.7 MP, but 18 effective MP and a size of 22.3 mm × 14.9 mm with an aspect ratio of 3:2. This means that the sensor captured 232.47 pixels per mm in width and 231.95 in height (dividing the number of pixels by the number of millimeters). In area: 53,919.7 pixels2/mm<sup>2</sup> . If photographs were taken at 80 cm from the walls, at a focal length of 25 mm, one would be working with just over three pixels/mm.

The problems of color characterization and exposure could be aggravated by the need to use natural light. The fact that the spaces were either diaphanous or almost diaphanous worked in our favor. The reference for our work was a color chart, such as Color Checker [45], which is often used in film shoots. In order to reduce the possibility of occlusions caused by over- or under-exposures, a fixed aperture was used to ensure a sufficient depth of field and low sensitivity in order to avoid problems with noise reading, and RAW files were also used in order to have the possibility of correcting the exposure values later [29,39,45].

Regarding the characters, the script conceived them as static figures, establishing situations and suggesting activities, but keeping them static so that the scenery would be the most prominent feature. The animation was applied to environmental or weather conditions, so that it would have an impact on the appearance of the surfaces. Research was done on the clothing, styling, and tools with which to dress the models, and they were asked to pose continuously in order to be captured by with photogrammetry methods, but on a *giratutto* and in controlled and constant lighting conditions.

In this phase, research was carried out on the assets that would be used to decorate the main hall. The initial documentation was collected precisely in the Alhambra's own museum, but a number of paintings set in the Nasrid period were also used.
