The Unified Modelling Language (UML) has become a commercially accepted standard for visualising software systems. Much of this success can be attributed to the computer aided software engineering (CASE) tools, which enable the UML to be effectively integrated into the software development life cycle. The UML is designed to be tool independent, however, in practice it would not be possible to manage the complexities of developing a large software system with "pencil and paper" UML diagrams. The UML is also designed to be extensible, allowing advanced use of visualisation such as 3D, however, in practice this extensibility is limited by the CASE tool used. With X3D-UML we present a means of using eXtensible 3D (X3D) as a visualisation medium for UML, enabling both standard and advanced visualisation to occur independent of CASE tools. We discuss the means, problems and benefits of transforming existing software system information into UML within an X3D environment.