From coin to 3D face sculpture portraits in the round of Roman emperors

Representing historical figures on visual media has always been a crucial aspect of political communication in the ancient world, as it is in modern society. A great example comes from ancient Rome, when the emperor's portraits were serially replicated on visual media to disseminate his image across the countries ruled by the Romans and to assert the power and authority that he embodied by making him universally recognizable. In particular, one of the most common media through which ancient Romans spread the imperial image was coinage, which showed a bi-dimensional projection of his portrait on the very low relief produced by the impression of the coin-die. In this work, we propose a new method that uses a multi-modal 2D and 3D approach to reconstruct the full portrait in the round of Roman emperors from their images adopted on ancient coins. A well-defined pipeline is introduced from the digitization of coins using 3D scanning techniques to the estimation of the 3D model of the portrait represented by a polygonal mesh. A morphable model trained on real 3D faces is exploited to infer the morphological (i.e., geometric) characteristics of the Roman emperor from the contours extracted from a coin portrait using a model fitting procedure. We present examples of face reconstruction of different emperors from coins produced in Rome as well as in the imperial provinces, which sometimes showed local variations of the official portraits centrally designed.