3D models of the lips for realistic speech animation

3D models of the lips have been developed in the framework of an audio visual articulatory speech synthesizer. Unlike most of the regions of the human face, the lips are essentially characterized by their border contours. The internal and external contours of the vermilion zone can be fitted by means of algebraic equations. The coefficients of these equations must be controlled so that the lip shape can be adapted to speaker dependent conformations and to any speech "gesture". To reach this goal, a 3D model of the lips has been based on a geometrical analysis of the natural lips of a French speaker. Our lip model was developed by adjusting a set of continuous functions best fitting the contours of 22 reference lip shapes. Only five parameters are necessary to predict all the equations of the contours of the lip model. From this model, a volumetric model based on implicit surfaces was also developed to take into account lip contact.