///\file "visualization/userVisAction/.README.txt"
///\brief Example userVisAction README page

/*! \page ExampleuserVisAction Example userVisAction

examples/extended/visualization/userVisAction

This example illustrates how to create a "vis action".

The idea is that you register a vis action with the vis manager and
activate it by a command /vis/scene/add/userAction.  In this case, it
draws a simple logo.

1) UVA_VisAction.cc defines a G4VUserVisAction and implements a Draw
   method.
      
2) In the main () program (see userVisAction.cc), UVA_VisAction is instantiated and
   its pointer registerd with the visualization manager. You may
   optionally specify an extent at this point to assist the viewers to
   locate the objects.

3) To visualise, use the usual Geant4 vis commands to create a view
   and scene, then add the vis action to the scene with
\verbatim
/vis/scene/add/userAction 
\endverbatim
   see vis.mac.

Note: The system needs an "extent" in order to point the virtual
camera and adjust its field of view, etc.  This defines the "standard
view".  You may zoom, etc., from this standard view.  The extent may
be specified as suggested above or by using /vis/scene/add/extent.


John Allison
27th November 2014

*/
