Abstract: Animating the geometry of a real-time character is typically done using fast methods such as smooth skinning or coarse physically-based animation. These methods are not able to capture realistic behaviors such as flesh and muscles bulging with constant volume or fine wrinkling of animated garments. This paper advocates the use of active geometric models, applied on top of the current geometric layer, to mimic these behaviors without requiring any expensive computation. Our models fit into the standard animation pipe-line and can be tuned in an intuitive way thanks to their geometric nature.