A 3D Face Coordinate System for Expression-Changed Pose Alignment

3D face data have been increased recently with the development of 3D data acquisition technology. 3D face has extensive applications. A proper coordinate system defined on faces is sometimes necessary. However, building a canonical coordinate system for all the 3D faces presenting the physiological vertical direction of human face is still an open question. In this paper, we propose a new 3D face canonical coordinate system based on the physiological structure of human face. Once locating the nose tip and finding the symmetry plane, we use the circular points on the face around the cheekbones to decide the front view, as the direction of the average normal of them is almost vertical to the center axis of human head. The experiment shows that our method is robust to rough data and provides a uniform description for all the 3D face models with different positions and expressions.