[vtkusers] Starting an animation with a keypress, terminating with another keypress

[John Platt]

Hi Steve,

You may find it simpler to check for an interrupt after rendering each frame. There has been some discussion on this recently in the list.

HTH

John.
  ----- Original Message ----- 
  From: Steve Chall 
  To: 'Jérôme' 
  Cc: vtkusers at vtk.org 
  Sent: Thursday, October 29, 2009 5:31 PM
  Subject: Re: [vtkusers] Starting an animation with a keypress,terminating with another keypress


  Jérôme,

  Yes, precisely: I need to create a new thread to do the animation, and interrupt that thread on the appropriate keypress.  Googling "vtk thread" now.  Thanks.

   

  -Steve

   


------------------------------------------------------------------------------

  From: Jérôme [mailto:jerome.velut at gmail.com] 
  Sent: Thursday, October 29, 2009 12:47 PM
  To: Steve Chall
  Cc: vtkusers at vtk.org
  Subject: Re: [vtkusers] Starting an animation with a keypress, terminating with another keypress

   

  Hi, 
  I think that the source of your problem is that when you press 'a', you enter an infinite loop from your main thread. You should call your Animate() function from another thread. I remember that VTK has built-in thread manager classes. It could be a solution.

  Hope that helps.
  Jerome

  2009/10/29 Steve Chall <stevec at renci.org>

  Dear fellow VTK enthusiasts:
  I'd like to trigger an animation from a keypress event, and then stop the
  animation with the same keypress event.  I've subclassed
  vtkInteractorStyleTrackballCamera with an OnKeyPress() method that looks a
  lot like what's included below.  When the user presses a key,
  myInteractorStyleTrackballCamera::OnKeyPress() is invoked, which (for the
  selected key, say 'a') toggles myObject's isAnimating Boolean flag.  If
  after toggling the flag is true, I want to start an animation loop.  If
  after toggling it's false, I want to stop that same loop.  But once I start
  the loop I can't penetrate with another 'a' keypress (or anything else other
  than a <Ctrl-C>) to change the flag back to false and thus stop the loop.
  How can I interrupt the "while (isAnimating)" loop once it starts?

  (I've also subclassed vtkRenderWindowInteractor because its Start() function
  seems like a place for interrupts, but I don't know what to do with it.)

  Thanks for any help you may be able to provide.

  -Steve Chall
   Senior Research Software Developer
   Renaissance Computing Institute
   Phone: 919-515-0051
   Email: stevec at renci.org

  // Pseudo C++ source code segments follow:

  ...
  myClass::Animate()
  {
   while (isAnimating)
   {
     this->RenderNextFrame();
   }
  }
  ...

  myClass *myObject = new myClass;

  ...
  void myInteractorStyleTrackballCamera::OnKeyPress()
  {
   switch (this->Interactor->GetKeyCode())
   {
     case 'a':
     case 'A':
       if (myObject)
       {
         myObject->isAnimating = !(myObject->isAnimating);

         if (myObject->isAnimating)
         {
           myObject->Animate();
         }
  /* This is sort of what I'd like to do:
         else
         {
           myObject->StopAnimating();
         }
       }
  */
       break;

     default:
       break;
   }

   vtkInteractorStyleTrackballCamera::OnKeyPress();
  }




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