WorldPointPicker

VTKExamples/Cxx/Interaction/WorldPointPicker


Description

This example demonstrates how to get the position of the point in 3D that is exactly behind the mouse click. This point is not likely a point that exists in the data set - i.e. it can be a point on the interior of a cell.

Code

WorldPointPicker.cxx

#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;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)

PROJECT(WorldPointPicker)

find_package(VTK REQUIRED)
include(${VTK_USE_FILE})

add_executable(WorldPointPicker MACOSX_BUNDLE WorldPointPicker.cxx )

target_link_libraries(WorldPointPicker ${VTK_LIBRARIES})

Download and Build WorldPointPicker

Click here to download WorldPointPicker and its CMakeLists.txt file. Once the tarball WorldPointPicker.tar has been downloaded and extracted,

cd WorldPointPicker/build 

If VTK is installed:

cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

make

and run it:

./WorldPointPicker

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.