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   Perform actions specified by the HUD. Define a data structure

   global DrawSCOutput
   DrawSCOutput = struct('zoomIn',0,'zoomOut',0,'plusY',0,...
                         'minusY',0,'plusZ',0,'minusZ')

   At the end of your simulation loop type

     DrawSCCntrl;
   end;

   This routine is called by a callback routine in DrawSC.m. You do not 
   normally call it yourself.

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   Form:
   DrawSCCntrl( action )
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   ------
   Inputs
   ------
   action    (1,:) Action to take

   -------
   Outputs
   -------
   None

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