SphereWidget

#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkPolyData.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkSphereWidget.h>
#include <vtkSphereRepresentation.h>
#include <vtkCommand.h>

class SphereCallback : public vtkCommand
{
  public:
    static SphereCallback *New()
    {
      return new SphereCallback;
    }
    SphereCallback(){}

    virtual void Execute(vtkObject *caller, unsigned long, void*)
    {

      vtkSphereWidget *sphereWidget = 
          reinterpret_cast<vtkSphereWidget*>(caller);

      double center[3];
      sphereWidget->GetCenter(center);
      std::cout << "Center: " << center[0] << " " << center[1] << " " << center[2] << std::endl;
    }

};

int main(int, char *[])
{
  // A renderer and render window
  vtkSmartPointer<vtkRenderer> renderer = 
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow = 
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);

  // An interactor
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = 
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);

  vtkSmartPointer<vtkSphereWidget> sphereWidget = 
    vtkSmartPointer<vtkSphereWidget>::New();
  sphereWidget->SetInteractor(renderWindowInteractor);
  sphereWidget->SetRepresentationToSurface();

  vtkSmartPointer<SphereCallback> sphereCallback = 
    vtkSmartPointer<SphereCallback>::New();

  sphereWidget->AddObserver(vtkCommand::InteractionEvent,sphereCallback);

  renderWindow->Render();
  renderWindowInteractor->Initialize();
  renderWindow->Render();
  sphereWidget->On();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(SphereWidget)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersSources
  vtkInteractionStyle
  vtkInteractionWidgets
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping SphereWidget: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(SphereWidget MACOSX_BUNDLE SphereWidget.cxx )
  target_link_libraries(SphereWidget PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(SphereWidget MACOSX_BUNDLE SphereWidget.cxx )
  target_link_libraries(SphereWidget PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS SphereWidget
    MODULES ${VTK_LIBRARIES}
    )
endif () 

cd SphereWidget/build 

cmake ..

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

make

./SphereWidget