SCENE GRAPH FOR DYNAMIC VIRTUAL ENVIRONMENT: SPANGRAPH
Résumé
The VRML (Virtual Reality Modeling Language) file format is a popular file format for describing a
graphical scene: object shapes, appearance properties, animation, and interactions. However, the format
does not provide any mechanism for describing the order of objects’ appearances or their changes over
time. Instead, an interface to Java is offered for controlling the temporal relationships between objects
in the scene.
The use of Java makes it difficult for a person with his programming skill to author a dynamic
virtual environment. In this paper we attach a span and an age to each object and their hierarchical and
temporal relations are expressed in a new data structure, called a span graph (SpanGraph). An object in
the span graph, when alive, grows its age and performs associated actions according to its age during the
extent of the time span. Furthermore, the object may have child objects whose spans are sub-extents of
the parent span. In this paper, we demonstrate uses of the SpanGraph in virtual studio and virtual
engineering design applications.