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Prototypes let authors define a new X3D node made up of other X3D nodes, extending the language for any scenes in new and interesting ways.
X3D extensibility includes a tremendous capability: authors can create prototype declarations and instances to define new X3D nodes. This is a powerful feature that puts the full power of this graphics language in the hands of Web authors. Prototype templates are themselves built using ProtoDeclare definitions or corresponding ExternProtoDeclare references. ProtoDeclare field definitions are found in the ProtoInterface tag, which can include multiple field declarations that define a name, initial value (if appropriate), accessType (inputOnly, outputOnly, initializeOnly and inputOutput) and type for each field. The IS and connect statements allow an internal field inside the ProtoBody to directly relay values and events via the exposed ProtoInterface field.
The node type of each ProtoDeclare is defined by the first node inside the ProtoBody declaration. Copies of a new node are created by name with ProtoInstance nodes. Default values for ProtoInstance fields can be overridden with fieldValue initializations. A ProtoInstance node can replace any other node in the scene graph having the same node type.
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