Abstract : In art, grouping plays a major role to convey relationships of objects and the organization of scenes. It is separated from style, which only determines how groups are rendered to achieve a visual abstraction of the depicted scene. We present an approach to interactively derive grouping information in a dynamic 3D scene. Our solution is simple and general. The resulting grouping information can be used as an input to any "rendering style". We provide an efficient solution based on an extended mean-shift algorithm customized by user-defined criteria. The resulting system is temporally coherent and real-time. The computational cost is largely determined by the scene's structure rather than by its geometric complexity.