Graphics objects consist of instances of one or more of the geometric objects (Curve, Surface, Mesh3d, etc.), and of objects to which they can be given to create a potential plot (Graph2d for Curves, Graph3d for Surfaces and/or Mesh3ds). A Graph object containing at least one geometric object needs to hand itself over to a third kind of object, a Plotter object, in order for the actual plot to appear somewhere (in an Xwindow or in a file, for example).