ISO/IEC 19775, Extensible 3D (X3D), defines a system that integrates 3D graphics and multimedia. Conceptually, each X3D file is a 3D time-based space that contains graphic and audio aural objects that can be dynamically modified through a variety of mechanisms.

This part of ISO/IEC 19776 defines a mapping of the abstract objects in X3D to a specific encoding using the technique defined in I14772-1 Virtual Reality Modeling Language (VRML97). ISO/IEC 14772 — Virtual reality modeling language (VRML).

Each Classic VRML-encoded X3D file:

1. supports all of the purposes of X3D files defined in ISO/IEC 19775; and
2. encodes X3D constructs in Classic VRML format.

An X3D file using the Classic VRML encoding A Classic VRML-encoded X3D file may be referenced from files using other X3D encodings, and may itself reference X3D files encoded using other X3D encodings. Such files can only be correctly processed by browsers which conform to all of the utilized encodings.