SphereWidget2

VTKEx/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.

Question

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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 =
      dynamic_cast<vtkSphereRepresentation*>( 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 =
    dynamic_cast<vtkSphereRepresentation*>( 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 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkInteractionStyle
  vtkvtkInteractionWidgets
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingOpenGL2 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.