  Volume Rendering applications require sophisticated user interaction for the
definition and refinement of transfer functions. Traditional 2D desktop user
interface elements have been developed to solve this task, but such concepts do
not map well to the interaction devices available in Virtual Reality
environments.
  In this paper, we propose an intuitive user interface for Volume Rendering
specifically designed for Virtual Reality environments. The proposed interface
allows transfer function design and refinement based on intuitive two-handed
operation of Wand-like controllers. Additional interaction modes such as
navigation and clip plane manipulation are supported as well.
  The system is implemented using the Sony PlayStation Move controller system.
This choice is based on controller device capabilities as well as application
and environment constraints.
  Initial results document the potential of our approach.
