Tecniche di modellazione 3D per una documentazione accurata delle incisioni rupestri: confronto tra Structure from Motion e Photometric Stereo

3D modelling represents a fundamental survey technique to represent archaeological evidence. It is particularly important to draw and analyse engravings because it is more descriptive and, somehow, objective than traditional drawings, which result interpretative and not replicable, becoming a debatable and often controversial matter. A technique able to verify the overlaying of signs is essential to establish the relative sequence, thus the chronology of engravings. However, the techniques are more than one and give different results. The paper tries to empirically compare SfM and PS methods to understand how they work surface representation and what are their specificities in a difficult context such as the Pianaùra engravings. The aim of the paper is to verify the accuracy of the techniques. Three paths are pursued: the first applies analyses of pure quantitative data, such as counting the number of points or faces built and so on; the second aims to verify quantitatively distortions by geometric measurements analysis; the third is a visual quality test, which focuses on users’ perception of 3D models. It can be concluded that the different fields of application and the different purposes of the research enhance the different specificities of the two techniques.