[vtkusers] continuous rendering from vtkVideoSource

[Tim Soper]

Hi-
I'm having trouble with the rendering frames acquired from vtkVideoSource. For now, I am simply trying to continuously display the random noise generated by the InternalGrab( ) method. I wrote a basic program that links the vtkImageViewer class to the vtkVideoSource. A ModifiedEvent observer is linked to a custom command in which I make a call to Render( ). This produces an error in a call to wglMakeCurrent. How should I properly link the render window to the video source? My code is below:

//CALLBACK
class vtkMyCallback : public vtkCommand
{
public:
  void SetRenderWindow( vtkRenderWindow* rw )
  { 
      renWin = rw;
  }
  static vtkMyCallback *New() 
    { return new vtkMyCallback; }
  virtual void Execute(vtkObject *caller, unsigned long, void*)
    {
        renWin->Render();  //THIS GENERATES MY ERROR
    }
private:
    vtkRenderWindow* renWin;
};

//MAIN
int main(int argc, char *argv[])
{
       ...

    //create the viewer and interactor
    vtkImageViewer* viewer = vtkImageViewer::New();
    vtkRenderWindowInteractor* iren = vtkRenderWindowInteractor::New();
    iren->SetRenderWindow( viewer->GetRenderWindow() );

    //create the video source
    vtkVideoSource * source = vtkVideoSource::New();
    source->SetFrameSize( 640, 480, 1 );  
    source->SetOutputFormatToLuminance();
    source->SetFrameRate(15);                               
    source->Initialize();

    //create the callback
    vtkMyCallback* callback = vtkMyCallback::New();
    callback->SetRenderWindow( viewer->GetRenderWindow() );

     //add an observer
    source->AddObserver( vtkCommand::ModifiedEvent, callback );

    //connect input to output
    viewer->SetInputConnection( source->GetOutputPort() );
    source->Record();

    iren->Initialize();
    iren->Start();

    iren->Delete();
    source->ReleaseSystemResources();
    source->Delete();
    viewer->Delete();

}

I believe my problem is that I am not calling Render from the main thread. I read a previous post (http://public.kitware.com/pipermail/vtkusers/2004-April/073478.html) that addressed a similar problem and the advised creating a new vtkMutexLock to communicate between main and the videoSource or "device" and the main thread. However, after reading this post I am unsure how to do this. Where should I create new vtkMutexLock? How do I connect it between the video source, the main thread, and say a interactor "Timer" Event observer. I guess I'm not sure where and how the threads change and where and how I should call the Render method forthe viewer. Please let me know if I am on the right track or if there is an easier way to do this.

Thanks
 
Tim 




 
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