An automatic process of predictive determination of the position and movements of the skin of a subject in a zone of interest, with the subject breathing freely or in an assisted manner, includes preliminarily acquiring multiple configurations of the skin profile in axial planes, at given successive times, in different respiratory positions, and for each axial plane, constructing at least one deformable digital model starting from different skin profiles, then noting, in a repetitive manner, the actual position of a point on the skin at the level of each axial plane, whose position is significantly modified during inhalation and exhalation phases, and providing, essentially in real time, a simulation of the skin profile in each axial plane, as a function of the actual position noted, and an evolving three-dimensional representation of the skin at the level of the zone of interest, by interpolation between the different axial planes.
