# WeightedTransformFilter

VTKExamples/Cxx/PolyData/WeightedTransformFilter

### Code

WeightedTransformFilter.cxx

    #include <vtkVersion.h>
    #include <vtkSphereSource.h>
    #include <vtkTransformFilter.h>
    #include <vtkProperty.h>
    #include <vtkCamera.h>
    #include <vtkFloatArray.h>
    #include <vtkPointData.h>
    #include <vtkPolyData.h>
    #include <vtkSmartPointer.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkTransform.h>
    #include <vtkWeightedTransformFilter.h>

    int main(int, char *[])
    {
      // Use a sphere as a basis of the shape
      vtkSmartPointer<vtkSphereSource> sphere =
        vtkSmartPointer<vtkSphereSource>::New();
      sphere->SetPhiResolution(40);
      sphere->SetThetaResolution(40);
      sphere->Update();

      vtkPolyData* sphereData = sphere->GetOutput();

      // Create a data array to hold the weighting coefficients
      vtkSmartPointer<vtkFloatArray> tfarray =
        vtkSmartPointer<vtkFloatArray>::New();
      vtkIdType npoints = sphereData->GetNumberOfPoints();
      tfarray->SetNumberOfComponents(2);
      tfarray->SetNumberOfTuples(npoints);

      // Parameterize the sphere along the z axis, and fill the weights
      // with (1.0-a, a) to linearly interpolate across the shape
      for(int i = 0; i < npoints; i++)
      {
        double pt[3];
        sphereData->GetPoint(i, pt);
    //    double x = pt[0];
    //    double y = pt[1];
        double z = pt[2];

        double zn = z + 0.5;
        double zn1 = 1.0 - zn;
        if(zn > 1.0)
        {
          zn = 1.0;
        }
        if(zn1 < 0.0)
        {
          zn1 = 0.0;
        }

        tfarray->SetComponent(i, 0, zn1);
        tfarray->SetComponent(i, 1, zn);
      }

      // Create field data to hold the array, and bind it to the sphere
    //  vtkSmartPointer<vtkFieldData> fd =
    //    vtkSmartPointer<vtkFieldData>::New();
      tfarray->SetName("weights");
      sphereData->GetPointData()->AddArray(tfarray);

      // Use an ordinary transform to stretch the shape
      vtkSmartPointer<vtkTransform> stretch =
        vtkSmartPointer<vtkTransform>::New();
      stretch->Scale(1, 1, 3.2);

      vtkSmartPointer<vtkTransformFilter> stretchFilter =
        vtkSmartPointer<vtkTransformFilter>::New();
    #if VTK_MAJOR_VERSION <= 5
      stretchFilter->SetInput(sphereData);
    #else
      stretchFilter->SetInputData(sphereData);
    #endif
      stretchFilter->SetTransform(stretch);

      // Now, for the weighted transform stuff
      vtkSmartPointer<vtkWeightedTransformFilter> weightedTrans =
        vtkSmartPointer<vtkWeightedTransformFilter>::New();

      // Create two transforms to interpolate between
      vtkSmartPointer<vtkTransform> identity =
        vtkSmartPointer<vtkTransform>::New();
      identity->Identity();

      vtkSmartPointer<vtkTransform> rotated =
        vtkSmartPointer<vtkTransform>::New();
      double rotatedAngle = 45;
      rotated->RotateX(rotatedAngle);

      weightedTrans->SetNumberOfTransforms(2);
      weightedTrans->SetTransform(identity, 0);
      weightedTrans->SetTransform(rotated, 1);
      // which data array should the filter use ?
      weightedTrans->SetWeightArray("weights");

      weightedTrans->SetInputConnection(stretchFilter->GetOutputPort());

      vtkSmartPointer<vtkPolyDataMapper> weightedTransMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      weightedTransMapper->SetInputConnection(weightedTrans->GetOutputPort());
      vtkSmartPointer<vtkActor> weightedTransActor =
        vtkSmartPointer<vtkActor>::New();
      weightedTransActor->SetMapper(weightedTransMapper);
      weightedTransActor->GetProperty()->SetDiffuseColor(0.8, 0.8, 0.1);
      weightedTransActor->GetProperty()->SetRepresentationToSurface();

      // Visualize
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);

      renderer->AddActor(weightedTransActor);
      renderer->SetBackground(0.1, 0.2, 0.5);
      renderWindow->SetSize(300, 300);

      renderer->ResetCamera();
      renderer->GetActiveCamera()->Azimuth(90);
      renderer->GetActiveCamera()->Dolly(1);

      renderWindow->Render();

      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(WeightedTransformFilter)

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

    add_executable(WeightedTransformFilter MACOSX_BUNDLE WeightedTransformFilter.cxx )

    target_link_libraries(WeightedTransformFilter ${VTK_LIBRARIES})

### Download and Build WeightedTransformFilter

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

    cd WeightedTransformFilter/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:

    ./WeightedTransformFilter

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.