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BIFS-Command Protocol

BIFS-Command protocol is used to send commands acting on a scene from a server to a client terminal in which the scene resides. A scene is a set of objects or nodes with specific behavior and an optional list of routes to propagate events between objects. A scene is represented by a scene graph in which leaves are nodes (this graph is the same as the one defined by VRML). Nevertheless, BIFS imposes some constraints on the scene graph:

  • It must start with only one top node. If you look at a VRML file, you will realize that you can have many top-level nodes such as Group or Transform.

  • All the routes must be at the end of the scene description. In VRML, they can be placed anywhere in the textual description of the scene.

  • As BIFS is a binary format, DEF names used in VRML for nodes are replaced by integers on a fixed number of bits. This means that references of such a node (in commands such as USE name and ROUTE name.field) are replaced by numeric identifiers.

  • ROUTEs can be DEF'd as nodes, which is not possible in VRML. This is used to reference routes when using commands.


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