/*=========================================================================

  Program:   Visualization Toolkit
  Module:    $RCSfile: Cone2.cxx,v $

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
//
// This example shows how to add an observer to a C++ program. It extends
// the Step1/Cxx/Cone.cxx C++ example (see that example for information on
// the basic setup). 
//
// VTK uses a command/observer design pattern. That is, observers watch for
// particular events that any vtkObject (or subclass) may invoke on
// itself. For example, the vtkRenderer invokes a "StartEvent" as it begins
// to render. Here we add an observer that invokes a command when this event
// is observed.
//

// first include the required header files for the vtk classes we are using
#include "vtkConeSource.h"
#include "vtkPolyDataMapper.h"
#include "vtkRenderWindow.h"
#include "vtkCommand.h"
#include "vtkCamera.h"
#include "vtkActor.h"
#include "vtkRenderer.h"

// Callback for the interaction
class vtkMyCallback : public vtkCommand
{
public:
  static vtkMyCallback *New() 
    { return new vtkMyCallback; }
  virtual void Execute(vtkObject *caller, unsigned long, void*)
    {
      vtkRenderer *renderer = reinterpret_cast<vtkRenderer*>(caller);
      cout << renderer->GetActiveCamera()->GetPosition()[0] << " "
           << renderer->GetActiveCamera()->GetPosition()[1] << " "
           << renderer->GetActiveCamera()->GetPosition()[2] << "\n";
    }
};

int main()
{
  //
  // The pipeline creation is documented in Step1
  //
  vtkConeSource *cone = vtkConeSource::New();
  cone->SetHeight( 3.0 );
  cone->SetRadius( 1.0 );
  cone->SetResolution( 10 );

  vtkPolyDataMapper *coneMapper = vtkPolyDataMapper::New();
  coneMapper->SetInputConnection( cone->GetOutputPort() );
  vtkActor *coneActor = vtkActor::New();
  coneActor->SetMapper( coneMapper );

  vtkRenderer *ren1= vtkRenderer::New();
  ren1->AddActor( coneActor );
  ren1->SetBackground( 0.1, 0.2, 0.4 );
  ren1->ResetCamera();

  vtkRenderWindow *renWin = vtkRenderWindow::New();
  renWin->AddRenderer( ren1 );
  renWin->SetSize( 300, 300 );

  // Here is where we setup the observer, we do a new and ren1 will
  // eventually free the observer
  vtkMyCallback *mo1 = vtkMyCallback::New();
  ren1->AddObserver(vtkCommand::StartEvent,mo1);
  mo1->Delete();
  
  //
  // now we loop over 360 degrees and render the cone each time
  //
  int i;
  for (i = 0; i < 360; ++i)
    {
    // render the image
    renWin->Render();
    // rotate the active camera by one degree
    ren1->GetActiveCamera()->Azimuth( 1 );
    }
  
  //
  // Free up any objects we created
  //
  cone->Delete();
  coneMapper->Delete();
  coneActor->Delete();
  ren1->Delete();
  renWin->Delete();

  return 0;
}