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.

Question

If you have a question about this example, please use the VTK Discourse Forum

Code¶

WorldPointPicker.cxx

#include <vtkActor.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkRendererCollection.h>
#include <vtkSphereSource.h>
#include <vtkWorldPointPicker.h>

namespace {

// Define interaction style.
class MouseInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
  static MouseInteractorStyle* New();
  vtkTypeMacro(MouseInteractorStyle, vtkInteractorStyleTrackballCamera);

  virtual void OnLeftButtonDown() override
  {
    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);

} // namespace

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  vtkNew<vtkSphereSource> sphereSource;
  sphereSource->Update();

  vtkNew<vtkWorldPointPicker> worldPointPicker;

  // Create a mapper and actor
  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(sphereSource->GetOutputPort());
  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetColor(colors->GetColor3d("MistyRose").GetData());

  // Create a renderer, render window, and interactor.
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("WorldPointPicker");

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetPicker(worldPointPicker);
  renderWindowInteractor->SetRenderWindow(renderWindow);

  vtkNew<MouseInteractorStyle> style;
  renderWindowInteractor->SetInteractorStyle(style);

  // Add the actor to the scene.
  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());

  // Render and interact.
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(WorldPointPicker)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  FiltersSources
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "WorldPointPicker: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(WorldPointPicker MACOSX_BUNDLE WorldPointPicker.cxx )
  target_link_libraries(WorldPointPicker PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS WorldPointPicker
  MODULES ${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.