# AffineWidget

VTKExamples/Cxx/Widgets/AffineWidget

### Description

This example demonstrates use of a vtkAffineWidget to apply transforms to a 3D prop in the x-y plane.

### Code

AffineWidget.cxx

    #include <vtkActor.h>
    #include <vtkAffineRepresentation2D.h>
    #include <vtkAffineWidget.h>
    #include <vtkAppendPolyData.h>
    #include <vtkCommand.h>
    #include <vtkInteractorStyleSwitch.h>
    #include <vtkPlaneSource.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>
    #include <vtkSphereSource.h>
    #include <vtkTransform.h>

    class vtkAffineCallback : public vtkCommand
    {
    public:
      static vtkAffineCallback *New()
        { return new vtkAffineCallback; }
      virtual void Execute(vtkObject *caller, unsigned long, void*);
      vtkAffineCallback():Actor(0),AffineRep(0)
      {
          this->Transform = vtkTransform::New();
      }
      ~vtkAffineCallback()
      {
          this->Transform->Delete();
      }
      vtkActor *Actor;
      vtkAffineRepresentation2D *AffineRep;
      vtkTransform *Transform;
    };

    void vtkAffineCallback::Execute(vtkObject*, unsigned long vtkNotUsed(event), void*)
    {
      this->AffineRep->GetTransform(this->Transform);
      this->Actor->SetUserTransform(this->Transform);
    }

    int main(int, char *[])
    {
      // Create two spheres: a larger one and a smaller one on top of the larger one
      // to show a reference point while rotating
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->Update();

      vtkSmartPointer<vtkSphereSource> sphereSource2 =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource2->SetRadius(0.075);
      sphereSource2->SetCenter(0,0.5,0);
      sphereSource2->Update();

      // Append the two spheres into one vtkPolyData
      vtkSmartPointer<vtkAppendPolyData> append =
        vtkSmartPointer<vtkAppendPolyData>::New();
      append->AddInputConnection(sphereSource->GetOutputPort());
      append->AddInputConnection(sphereSource2->GetOutputPort());

      // Create a plane centered over the larger sphere with 4x4 sub sections
      vtkSmartPointer<vtkPlaneSource> planeSource =
        vtkSmartPointer<vtkPlaneSource>::New();
      planeSource->SetXResolution(4);
      planeSource->SetYResolution(4);
      planeSource->SetOrigin(-1,-1,0);
      planeSource->SetPoint1(1,-1,0);
      planeSource->SetPoint2(-1,1,0);

      // Create a mapper and actor for the plane: show it as a wireframe
      vtkSmartPointer<vtkPolyDataMapper> planeMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      planeMapper->SetInputConnection(planeSource->GetOutputPort());
      vtkSmartPointer<vtkActor> planeActor =
        vtkSmartPointer<vtkActor>::New();
      planeActor->SetMapper(planeMapper);
      planeActor->GetProperty()->SetRepresentationToWireframe();
      planeActor->GetProperty()->SetColor(1,0,0);

      // Create a mapper and actor for the spheres
      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(append->GetOutputPort());
      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      // Create a renderer and render window
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      renderer->AddActor(actor);
      renderer->AddActor(planeActor);
      renderer->GradientBackgroundOn();
      renderer->SetBackground(1,1,1);
      renderer->SetBackground2(0,0,1);

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

      // Create an affine widget to manipulate the actor
      // the widget currently only has a 2D representation and therefore applies transforms in the X-Y plane only
      vtkSmartPointer<vtkAffineWidget> affineWidget =
        vtkSmartPointer<vtkAffineWidget>::New();
      affineWidget->SetInteractor(renderWindowInteractor);
      affineWidget->CreateDefaultRepresentation();
      vtkAffineRepresentation2D::SafeDownCast(affineWidget->GetRepresentation())->PlaceWidget(actor->GetBounds());

      vtkSmartPointer<vtkAffineCallback> affineCallback =
          vtkSmartPointer<vtkAffineCallback>::New();
      affineCallback->Actor = actor;
      affineCallback->AffineRep = vtkAffineRepresentation2D::SafeDownCast(affineWidget->GetRepresentation());

      affineWidget->AddObserver(vtkCommand::InteractionEvent,affineCallback);
      affineWidget->AddObserver(vtkCommand::EndInteractionEvent,affineCallback);

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

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(AffineWidget)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(AffineWidget MACOSX_BUNDLE AffineWidget.cxx)

    target_link_libraries(AffineWidget ${VTK_LIBRARIES})

### Download and Build AffineWidget

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

    cd AffineWidget/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:

    ./AffineWidget

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