Döllner, Jürgen; Hinrichs, Klaus
The Journal of Visualization and Computer Animation (JVCA)
We present an object-oriented 3D graphics and animation framework which provides a new methodology for the symmetric modeling of geometry and behavior. The toolkit separates the specification of geometry and behavior by two types of directed acyclic graphs, the geometry graph and the behavior graph, which are linked together through constraint relations. All geometry objects and behavior objects are represented as DAG nodes. The geometry graph provides a renderer-independent hierarchical description of 3D scenes and rendering processes. The behavior graph specifies time- and event-dependent constraints applied to graphics objects. Behavior graphs simplify the specification of complex animations and 3D interactions by providing nodes for the management of the time and event flow (e.g. durations, time layouts, time repeaters, actions). Nodes contain, manipulate and share instances of constrainable graphical abstract data types. Geometry nodes and behavior nodes are used to configure high-level 3D widgets, i.e. highlevel building blocks for constructing 3D applications. The fine-grained object structure of the system leads to an extensible reusable framework which can be implemented efficiently.