More interesting than the predefined objects, IVL allows the creation of new classes by simply giving IVL the name of a file or URL which holds a scene graph. Since IVL allows Inventor scene graphs to be read in, this is a way to extend the basic set of allowed nodes in VRML. That is, one can model with NURBS-based shapes or any other Inventor-supported node, as still be able to manipulate these objects and generate valid VRML as output. IVL allows you to name the type of these objects for future reference, much like the VRML concept of DEF. For example,
class Pear = "http://fruit.org/bartlett.wrl"This ability to define classes from pre-existing scenes allows complex scenes to be created and manipulated just as easily as simple scenes. The ability to reference VRML files through their URL, couples with publically-available repositories of VRML models, makes IVL a modeling tool. IVL also supports gzip compressed files, useful for reducing download times.