## 5 Discussion  
This paper analyzes the possibility of protecting a digitized sculpture using a new approach. Clay was added to the sculpture at locations selected by the sculptor. Then, the original sculpture and the sculpture with added clay were digitized in two ways, using photogrammetry and 3D scanning. By comparing the results obtained by photogrammetric surveying and scanning of the sculpture with structured light, when determining the error between the original and models with embedded digital protection, we came to the conclusion that this error is visually equally noticeable in models obtained using both 3D digitization techniques. This shows that photogrammetry and structured light can be used to analyze the comparison of the two models, but in this case when comparing a smaller object such as a sculpture, it is better to use 3D scanning because the result is a sculpture with fewer irregularities on the surface, as other authors have previously concluded. When comparing the models obtained by photogrammetry and scanning, the situation is real because all three places where clay was added are noted, and the measures of the added material in both cases correspond to the real situation. As part of this research, a survey of 195 subjects was conducted where four sculptures were observed, an original 3D model (sculpture 1), a model with a digital error (sculpture 4), and two more 3D models (sculptures 2 and 3) obtained by deformation of the original model in Zbrush software (Figure 15). However, the survey used a 3D model obtained by 3D scanning because its surface is smoother. For research purposes, a turntable video was created in which these four sculptures rotate simultaneously, each around its own vertical axis, and based on that, a seven-question survey was conducted. Of the total number of respondents, 13.3% claimed that there were two identical sculptures, and of that 13.3%, 76% claimed that sculptures 1 and 4 were the same. Moreover, out of the total number, 86.7% of the respondents said that there were no two identical sculptures, and out of that number, 64.9% noticed that sculptures 1 and 4 are the most similar. In both groups (13.3% and 86.7%), it was predominantly observed that sculptures 1 and 4 were the same or most similar. This result shows us that the digital error created in collaboration with the sculptor was introduced with a measure that is difficult to visually notice. It is much easier to  
Figure 18: Digital protection extraction using 3 ds Max software as a subtraction between the protected and the original 3D sculpture. notice an error that is obtained by moving the vertex in a 3D software without an adequate strategy. Our strategy was that the sculptor would add a protection that would be difficult to notice visually. The answers of the respondents fulfilled our expectations because they noticed that the most similar sculptures are the original and the sculpture with a digital error, which corresponds to the real situation. The basic idea of this research is to make a 3D model with a digital error available to the public, while the original 3D model is hidden from the public. The average observer will not be deprived of their artistic experience of the sculpture because they are not even aware that it has been minimally altered in relation to the original, and the owners of the sculpture are thus protected from the potential abuse of their work. Additionally, our intention was to present to the general public a 3D model of the sculpture that is very similar to the original, but that is not the original. In that way, the observers of this model would not be deprived at all of the artistic experience of the observed work of art. The other advantage of this approach is that there is no possibility of abuse of the original work of art. If someone takes the 3D model of the sculpture that we have given for public inspection, and prints that model on a 3D printer, we could easily prove that such a sculpture is a forgery.