This work presents a methodology for 3D modeling of lip motion in speech production and its application to lip tracking and visual speech animation. Firstly, a geometric modeling allows to create a 3D lip model from 30 control points for any lip shape. Secondly, a statistical analysis, performed on a set of 10 key shapes, generates a lip gesture coding with three articulatory-oriented parameters, specific to one speaker. The choice of the key shapes is based on general phonetic observations. Finally, the application for lip tracking of the 3D model controlled by the three parameters is presented and evaluated.