BoxWidget2

Description¶

This example uses a vtkBoxWidget2 to manipulate an actor. The widget only contains the interaction logic; the actual box is drawn by the accompanying vtkBoxRepresentation. Contrary to the older vtkBoxWidget, this widget doesn't provide functionality to assign it to one or more actors, so that has to be implemented manually. The box is dimensioned and positioned by passing a bounding box to PlaceWidget method, with the SetPlaceFactor method providing a scaling factor in relation to that bounding box. The transformations applied to the box can be used to manipulate any number of object(s), via a custom callback class, which is passed to the box widget through the AddObserver method.

The older implementation vtkBoxWidget provides functionality to receive a vtkProp3D for the initial positioning and sizing, but the transformation synchronization still needs to be done manually. See BoxWidget for a simple example of how to use it.

Code¶

BoxWidget2.cxx

#include <vtkSmartPointer.h>
// For the rendering pipeline setup:
#include <vtkConeSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkInteractorStyleTrackballCamera.h>
// For vtkBoxWidget2:
#include <vtkBoxWidget2.h>
#include <vtkBoxRepresentation.h>
#include <vtkCommand.h>
#include <vtkTransform.h>

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

  vtkSmartPointer<vtkActor> m_actor;

  void SetActor( vtkSmartPointer<vtkActor> actor )
  {
    m_actor = actor;
  }

  virtual void Execute( vtkObject *caller, unsigned long, void* )
  {
    vtkSmartPointer<vtkBoxWidget2> boxWidget =
      dynamic_cast<vtkBoxWidget2*>(caller);

    vtkSmartPointer<vtkTransform> t =
      vtkSmartPointer<vtkTransform>::New();

    dynamic_cast<vtkBoxRepresentation*>( boxWidget->GetRepresentation() )->GetTransform( t );
    this->m_actor->SetUserTransform( t );
  }

  vtkBoxCallback(){}
};

int main( int vtkNotUsed( argc ), char* vtkNotUsed( argv )[] )
{
  vtkSmartPointer<vtkConeSource> coneSource =
    vtkSmartPointer<vtkConeSource>::New();
  coneSource->SetHeight( 1.5 );

  vtkSmartPointer<vtkPolyDataMapper> mapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  mapper->SetInputConnection( coneSource->GetOutputPort() );

  vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
  actor->SetMapper( mapper );

  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderer->AddActor(actor);
  renderer->ResetCamera(); // Reposition camera so the whole scene is visible

  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer( renderer );

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

  // Use the "trackball camera" interactor style, rather than the default "joystick camera"
  vtkSmartPointer<vtkInteractorStyleTrackballCamera> style =
    vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New();
  renderWindowInteractor->SetInteractorStyle( style );

  vtkSmartPointer<vtkBoxWidget2> boxWidget =
    vtkSmartPointer<vtkBoxWidget2>::New();
  boxWidget->SetInteractor( renderWindowInteractor );
  boxWidget->GetRepresentation()->SetPlaceFactor( 1 ); // Default is 0.5
  boxWidget->GetRepresentation()->PlaceWidget(actor->GetBounds());

  // Set up a callback for the interactor to call so we can manipulate the actor
  vtkSmartPointer<vtkBoxCallback> boxCallback =
    vtkSmartPointer<vtkBoxCallback>::New();
  boxCallback->SetActor(actor);
  boxWidget->AddObserver( vtkCommand::InteractionEvent, boxCallback );

  boxWidget->On();

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(BoxWidget2)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonTransforms
  vtkFiltersSources
  vtkInteractionStyle
  vtkInteractionWidgets
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping BoxWidget2: ${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(BoxWidget2 MACOSX_BUNDLE BoxWidget2.cxx )
  target_link_libraries(BoxWidget2 PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(BoxWidget2 MACOSX_BUNDLE BoxWidget2.cxx )
  target_link_libraries(BoxWidget2 PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS BoxWidget2
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build BoxWidget2¶

Click here to download BoxWidget2 and its CMakeLists.txt file. Once the tarball BoxWidget2.tar has been downloaded and extracted,

cd BoxWidget2/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:

./BoxWidget2

WINDOWS USERS

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