# SphereWidget2

VTKExamples/Cxx/Widgets/SphereWidget2

### Description

The spherical coordinates of the widget's handle match the coordinates that it displays in the window. The world coordinates of the handle are also shown.

### Code

SphereWidget2.cxx

    #include <vtkCommand.h>
    #include <vtkMath.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>
    #include <vtkSphere.h>
    #include <vtkSphereRepresentation.h>
    #include <vtkSphereWidget2.h>

    // Callback that displays the sphere widget's spherical handle postion
    // in both sphercial (relative to the widget's center) and cartesian global coordinates
    class vtkSphereCallback : public vtkCommand
    {
    public:
      static vtkSphereCallback *New()
      {
        return new vtkSphereCallback;
      }

      virtual void Execute(vtkObject *caller, unsigned long, void*)
      {
        vtkSphereWidget2 *sphereWidget =
          reinterpret_cast<vtkSphereWidget2*>(caller);

        double center[3], handlePosition[3];
        vtkSphereRepresentation* sphereRepresentation =
          vtkSphereRepresentation::SafeDownCast( sphereWidget->GetRepresentation() );
        sphereRepresentation->GetHandlePosition( handlePosition );
        sphereRepresentation->GetSphere( this->Sphere );

        this->Sphere->GetCenter( center );

        double radius = sqrt( static_cast<double>(vtkMath::Distance2BetweenPoints( center, handlePosition ) ) );
        radius = (radius <= 0.0 ? 1.0 : radius );
        double theta = vtkMath::DegreesFromRadians( atan2( ( handlePosition[1] - center[1] ), ( handlePosition[0] - center[0] ) ) );
        double phi   = vtkMath::DegreesFromRadians( acos( ( handlePosition[2] - center[2] ) / radius ) );

        std::cout << "r, theta, phi: ("
                  << std::setprecision(3)
                  << radius << ", " << theta << ", " << phi << ") "
                  << "x, y, z: ("
                  << handlePosition[0] << ", "
                  << handlePosition[1] << ", "
                  << handlePosition[2] << ") "
                  << std::endl;
      }

      vtkSphereCallback(){ this->Sphere = vtkSphere::New(); }
      ~vtkSphereCallback(){ this->Sphere->Delete(); }

      vtkSphere* Sphere;
    };

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

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

      // Create a sphere widget
      vtkSmartPointer<vtkSphereWidget2> sphereWidget =
        vtkSmartPointer<vtkSphereWidget2>::New();
      sphereWidget->SetInteractor(renderWindowInteractor);
      sphereWidget->CreateDefaultRepresentation();

      vtkSphereRepresentation* sphereRepresentation =
        vtkSphereRepresentation::SafeDownCast( sphereWidget->GetRepresentation() );
      sphereRepresentation->HandleVisibilityOn();

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

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

      renderWindow->Render();

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

      // Begin mouse interaction
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(SphereWidget2)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkInteractionStyle
      vtkInteractionWidgets
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping SphereWidget2: ${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(SphereWidget2 MACOSX_BUNDLE SphereWidget2.cxx )
      target_link_libraries(SphereWidget2 PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(SphereWidget2 MACOSX_BUNDLE SphereWidget2.cxx )
      target_link_libraries(SphereWidget2 PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS SphereWidget2
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build SphereWidget2

Click here to download SphereWidget2 and its CMakeLists.txt file. Once the tarball SphereWidget2.tar has been downloaded and extracted,

    cd SphereWidget2/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:

    ./SphereWidget2

WINDOWS USERS

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