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Chapter 19. CUSTOMIZING VRML FOR BIFS > Converting VRML Contents to BIFS

Converting VRML Contents to BIFS

In earlier chapters you learned about BIFS-Commands and BIFS-Anim protocols. BIFS-Commands adds some constraints in the VRML scene:

  • Scenes must start with a top-level node. In the case of VRML contents it can only be a Group node. All nodes must be children of this top-level node. Adding a Group on top of each VRML content does not change the functionalities of the scene.

  • All ROUTEs must be put at the end of the scene description.

  • DEF names must be converted to unique integer identifiers. The easiest way to do this is to create and maintain a hash table with keys as DEF names and values as identifiers. Each time a new DEF name is encountered, the identifier number is incremented. When a VRML command using DEF names such as USE or ROUTE is parsed, the identifier corresponding to the DEF name is already in the hash table.


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