# CutWithScalars

VTKExamples/Cxx/VisualizationAlgorithms/CutWithScalars

### Code

CutWithScalars.cxx

    #include <vtkSmartPointer.h>
    #include <vtkXMLPolyDataReader.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkPolyData.h>
    #include <vtkDoubleArray.h>
    #include <vtkPoints.h>
    #include <vtkPointData.h>
    #include <vtkPlane.h>
    #include <vtkProperty.h>
    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>

    #include <vtkContourFilter.h>

    int main(int argc, char *argv[])
    {
      if (argc < 2)
      {
        std::cout << "Usage: " << argv[0]
                  << " inputFilename(.vtp) [numberOfCuts]" << std::endl;
        return EXIT_FAILURE;
      }
      std::string inputFilename = argv[1];

      int numberOfCuts = 10;
      if (argc > 2)
      {
        numberOfCuts = atoi(argv[2]);
      }

      vtkSmartPointer<vtkXMLPolyDataReader> reader =
        vtkSmartPointer<vtkXMLPolyDataReader>::New();
      reader->SetFileName(inputFilename.c_str());
      reader->Update();

      double bounds[6];
      reader->GetOutput()->GetBounds(bounds);
      std::cout << "Bounds: "
                << bounds[0] << ", " << bounds[1] << " "
                << bounds[2] << ", " << bounds[3] << " "
                << bounds[4] << ", " << bounds[5] << std::endl;

      vtkSmartPointer<vtkPlane> plane =
        vtkSmartPointer<vtkPlane>::New();
      plane->SetOrigin((bounds[1] + bounds[0]) / 2.0,
                       (bounds[3] + bounds[2]) / 2.0,
                       (bounds[5] + bounds[4]) / 2.0);
      plane->SetNormal(0,0,1);

      // Create Scalars
      vtkSmartPointer<vtkDoubleArray> scalars =
        vtkSmartPointer<vtkDoubleArray>::New();
      int numberOfPoints = reader->GetOutput()->GetNumberOfPoints();
      scalars->SetNumberOfTuples(numberOfPoints);
      vtkPoints *pts = reader->GetOutput()->GetPoints();
      for (int i = 0; i < numberOfPoints; ++i)
      {
        double point[3];
        pts->GetPoint(i, point);
        scalars->SetTuple1(i, plane->EvaluateFunction(point));
      }
      reader->GetOutput()->GetPointData()->SetScalars(scalars);
      reader->GetOutput()->GetPointData()->GetScalars()->GetRange();

      // Create cutter
      vtkSmartPointer<vtkContourFilter> cutter =
        vtkSmartPointer<vtkContourFilter>::New();
      cutter->SetInputConnection(reader->GetOutputPort());
      cutter->ComputeScalarsOff();
      cutter->ComputeNormalsOff();
      cutter->GenerateValues(
        numberOfCuts,
        .99 * reader->GetOutput()->GetPointData()->GetScalars()->GetRange()[0],
        .99 * reader->GetOutput()->GetPointData()->GetScalars()->GetRange()[1]);

      vtkSmartPointer<vtkPolyDataMapper> cutterMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      cutterMapper->SetInputConnection( cutter->GetOutputPort());
      cutterMapper->ScalarVisibilityOff();

      // Create cut actor
      vtkSmartPointer<vtkActor> cutterActor =
        vtkSmartPointer<vtkActor>::New();
      cutterActor->GetProperty()->SetColor(1.0,1,0);
      cutterActor->GetProperty()->SetLineWidth(2);
      cutterActor->SetMapper(cutterMapper);

      // Create model actor
      vtkSmartPointer<vtkPolyDataMapper> modelMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      modelMapper->SetInputConnection( reader->GetOutputPort());
      modelMapper->ScalarVisibilityOff();

      vtkSmartPointer<vtkActor> modelActor =
        vtkSmartPointer<vtkActor>::New();
      modelActor->GetProperty()->SetColor(0.5,1,0.5);
      modelActor->SetMapper(modelMapper);

      // Create renderers and add actors of plane and model
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->AddActor(cutterActor);
      renderer->AddActor(modelActor);

      // Add renderer to renderwindow and render
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      renderWindow->SetSize(600, 600);

      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);
      renderer->SetBackground(.2, .3, .4);

      renderer->GetActiveCamera()->SetPosition(0, -1, 0);
      renderer->GetActiveCamera()->SetFocalPoint(0, 0, 0);
      renderer->GetActiveCamera()->SetViewUp(0, 0, 1);
      renderer->GetActiveCamera()->Azimuth(30);
      renderer->GetActiveCamera()->Elevation(30);

      renderer->ResetCamera();
      renderWindow->Render();

      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(CutWithScalars)

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

    add_executable(CutWithScalars MACOSX_BUNDLE CutWithScalars.cxx)

    target_link_libraries(CutWithScalars ${VTK_LIBRARIES})

### Download and Build CutWithScalars

Danger

The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.

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

    cd CutWithScalars/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:

    ./CutWithScalars

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.