Director is a powerful authoring system. It uses the metaphor of a timeline with tracks for each stream, such as audio or video. The timeline is broken into frames, so one can construct an animation by specifying the beginning location of an object, its ending location, and the method of interpolation to fill in the gaps. Members of the cast can be moved around on an image that is chosen for the background. Movies or other time-based performances (e.g., using QuickTime or a previous Director movie) can be placed onto a track for inclusion. Special effects allow smooth transitions.