VTK/Examples/Cxx/Interaction/WorldPointPicker

#include <vtkSmartPointer.h>
#include <vtkRendererCollection.h>
#include <vtkWorldPointPicker.h>
#include <vtkSphereSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkActor.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkObjectFactory.h>
 
// Define interaction style
class MouseInteractorStyle : public vtkInteractorStyleTrackballCamera
{
  public:
    static MouseInteractorStyle* New();
    vtkTypeMacro(MouseInteractorStyle, vtkInteractorStyleTrackballCamera);
 
    virtual void OnLeftButtonDown() 
    {
 
      std::cout << "Picking pixel: " << this->Interactor->GetEventPosition()[0] << " " << this->Interactor->GetEventPosition()[1] << std::endl;
      this->Interactor->GetPicker()->Pick(this->Interactor->GetEventPosition()[0], 
                         this->Interactor->GetEventPosition()[1], 
                         0,  // always zero.
                         this->Interactor->GetRenderWindow()->GetRenderers()->GetFirstRenderer());
      double picked[3];
      this->Interactor->GetPicker()->GetPickPosition(picked);
      std::cout << "Picked value: " << picked[0] << " " << picked[1] << " " << picked[2] << std::endl;
      // Forward events
      vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
    }
 
};
vtkStandardNewMacro(MouseInteractorStyle);
 
int main(int, char *[])
{
  vtkSmartPointer<vtkSphereSource> sphereSource = 
    vtkSmartPointer<vtkSphereSource>::New();
  sphereSource->Update();
 
  vtkSmartPointer<vtkWorldPointPicker> worldPointPicker = 
    vtkSmartPointer<vtkWorldPointPicker>::New();
 
  // Create a mapper and actor
  vtkSmartPointer<vtkPolyDataMapper> mapper = 
    vtkSmartPointer<vtkPolyDataMapper>::New();
  mapper->SetInputConnection(sphereSource->GetOutputPort());
  vtkSmartPointer<vtkActor> actor = 
    vtkSmartPointer<vtkActor>::New();
  actor->SetMapper(mapper);
 
  // Create a renderer, render window, and interactor
  vtkSmartPointer<vtkRenderer> renderer = 
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow = 
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = 
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetPicker(worldPointPicker);
  renderWindowInteractor->SetRenderWindow(renderWindow);
 
  vtkSmartPointer<MouseInteractorStyle> style = 
    vtkSmartPointer<MouseInteractorStyle>::New();
  renderWindowInteractor->SetInteractorStyle( style );
 
  // Add the actor to the scene
  renderer->AddActor(actor);
  renderer->SetBackground(1,1,1); // Background color white
 
  // Render and interact
  renderWindow->Render();
  renderWindowInteractor->Start();
 
  return EXIT_SUCCESS;
}