A model for compression and classification of face data structures

In this paper we present a 3-D model with physical properties which simplifies the analysis and the synthesis of deformable faces and solids. Our model presents three relevant particularities. First, it describes the external envelope of faces with 1-D finite elements assembled with a new 3-connected mesh topology. Second, the mesh deformations are analysed with a modal analysis. Because our model associates these two particularities, the number of rigid modes given by the modal analysis is equal to the number of 1-D finite elements, which is also the half of the number of Degrees of Freedom (DOF). This number of rigid modes is a basic characteristic of our model. The second half of modes constitutes the nonrigid modes. Third, we use these rigid modes and the first nonrigid mode to synthesize a mean face named a photo-fit identikit or class, around which we synthesize face varieties by action on secondary nonrigid modes. Our physical 3-D model allows compression of face data structures because a greater number of secondary nonrigid modes can be suppressed to define a class or its varieties, and because the synthesis of varieties does not need more information storage than their classes. Our physical 3-D model allows classification of face data structures because we can associate an objective measure to each synthesized face. We can measure the deformation between a variety and its photo-fit identikit.