The X3D library is used to load an X3D file and render it using OpenGL (an X3D file is an XML file describing a 3D environment that can be rendered with OpenGL.) The library supports all the objects as defined in the X3D specification in 2006. The render library is still somewhat limited, though. It works well under Linux. It is likely to work on any Unix, and has worked under MS Windows before. The project includes a test that makes use of FLTK version 2.0-m3. That version of FLTK can be downloaded from the project repository, as FLTK itself actually ended up not publishing a concrete 2.0 version of the library.