Ubit is a new GUI toolkit that combines the advantages of scene graph and
widget based toolkits. The Ubit3D extension makes it possible to display 2D GUIs
in a 3D space. Main features:
* Molecular architecture: a flexible achitecture that makes it possible to
  customize widgets in a simple way without having to create new classes.
* Pseudo declarative API: applications can either be created by using a
  classical OO API or a pseudo-declarative API that makes programming much
  simpler. Both APIs are written in the C++ language.
* Multiple displays on remote hosts: replication of widget graphs on
  remote hosts: applications can open windows on several displays
* Multiple pointers: supports multiple pointers and two-handed interaction.
  Applications can handle multiple event flows that are logically
  separated (hence, events coming from different threads won't be merged).
* OpenGL and 3D interfaces: Ubit can display 2D interfaces in a 3D space.
  These interfaces are directly rendered in 3D by using OpenGL.
* Advanced graphical features: provides support for multiscale interfaces,
  semantic zooming, transparent and transluscent widgets,
  magic lenses, see-through tools, Control menus, XHTML parsing and rendering...
