3D orientation of archaeological fragments coming from a Gothic spire

In this paper, we address the problem of 3D mesh orientation applied to archaeological fragments coming from a Gothic spire. Initially, these fragments are handled leading to their deterioration while the accuracy of measures (distances, molding shape,. . . ) is not always relevant. To facilitate their study, a 3D acquisition process is applied on these fragments to work on their virtual representations and computerised tools can be proposed. One of them consists in finding the orientation of a 3D mesh. Unfortunately, existing methods provide unexpected results. This is mainly due to the presence of ornamentations we can assimilate to outliers. Therefore, we propose a new method based on the identification of significant areas on the 3D mesh and on the determination of their associated orientation by considering differential parameters. Then, a voting method is performed to identify the orientation appearing the most frequently. Applied on the fragments, we obtain successful results allowing to go further in their analysis.