When bound, the tool changes its visual appearance to a shape that provides information about its behavior and offers semantic feedback. During manipulation, the tool's and the application object's constraint networks remain continuously connected, so as to ensure information propagation. Multiple tools can be active simultaneously in the same 3D environment in order to control all its aspects. The environment's consistency is continuously ensured by the underlying constraint solver. The bi-directionality of the relationships between user-interface and application objects makes it possible to use virtual tools to interact with a dynamic environment, opening the door to the integration of animation and interaction techniques.