Can the scene description be changed?
The scene description can be dynamically changed at any time. An initial scene description is provided at the beginning of an MPEG-4 stream. It can be as simple as a single node, or as complex as one wants (within limits that are established for ensuring conformance). BIFS-Commands are used to modify a set of properties of the scene at a given time. It is possible to insert, delete and replace nodes, fields and ROUTEs as well as to replace the entire scene. For continuous changes of the parameters of the scene, BIFS-Anim can be used; it specifically addresses the continuous update of the fields of a particular node. BIFS-Anim is used to integrate different kinds of animation, including the ability to animate face models as well as meshes, 2D and 3D positions, rotations, scale factors, and color attributes. The BIFS-Anim information is conveyed in its own elementary stream.
