  Prototyping is an important part in research and development of tangible user
interfaces (TUIs). On the way from the idea to a working prototype, new
hardware prototypes usually have to be crafted repeatedly in numerous
iterations. This brings us to think about virtual prototypes that exhibit the
same functionality as a real TUI, but reduce the amount of time and resources
that have to be spent.
  Building upon existing open-source software - the middleware Robot Operating
System (ROS) and the 3D simulator Gazebo - we have created a toolkit that can
be used for developing and testing fully functional implementations of a
tangible user interface as a virtual device. The entire interaction between the
TUI and other hardware and software components is controlled by the middleware,
while the human interaction with the TUI can be explored using the 3D simulator
and 3D input/output technologies. We argue that by simulating parts of the
hardware-software co-design process, the overall development effort can be
reduced.
