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# IsoContours

VTKEx/Cxx/ImplicitFunctions/IsoContours

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See (CSharp)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

IsoContours.cxx

    #include <vtkSmartPointer.h>
    #include <vtkContourFilter.h>

    #include <vtkInteractorStyleUser.h>
    #include <vtkProperty.h>
    #include <vtkOutlineFilter.h>
    #include <vtkCommand.h>
    #include <vtkSliderWidget.h>
    #include <vtkSliderRepresentation.h>
    #include <vtkSliderRepresentation3D.h>
    #include <vtkImageData.h>
    #include <vtkCellArray.h>
    #include <vtkFloatArray.h>
    #include <vtkPointData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkXMLImageDataWriter.h>
    #include <vtkNamedColors.h>

    namespace
    {
    void CreateData(vtkImageData* data);

    class vtkSliderCallback : public vtkCommand
    {
    public:
      static vtkSliderCallback *New()
      {
        return new vtkSliderCallback;
      }
      virtual void Execute(vtkObject *caller, unsigned long, void*)
      {
        vtkSliderWidget *sliderWidget =
          reinterpret_cast<vtkSliderWidget*>(caller);
        double value = static_cast<vtkSliderRepresentation *>(sliderWidget->GetRepresentation())->GetValue();
        this->ContourFilter->GenerateValues(1, value, value);

      }
      vtkSliderCallback():ContourFilter(NULL) {}
      vtkContourFilter* ContourFilter;
    };
    }

    int main(int, char *[])
    {
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      vtkSmartPointer<vtkImageData> data =
        vtkSmartPointer<vtkImageData>::New();
      CreateData(data);

      // Create an isosurface
      vtkSmartPointer<vtkContourFilter> contourFilter =
        vtkSmartPointer<vtkContourFilter>::New();
      contourFilter->SetInputData(data);
      contourFilter->GenerateValues(1, 10, 10); // (numContours, rangeStart, rangeEnd)

      // Map the contours to graphical primitives
      vtkSmartPointer<vtkPolyDataMapper> contourMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      contourMapper->SetInputConnection(contourFilter->GetOutputPort());

      // Create an actor for the contours
      vtkSmartPointer<vtkActor> contourActor =
        vtkSmartPointer<vtkActor>::New();
      contourActor->SetMapper(contourMapper);
      contourActor->GetProperty()->SetLineWidth(5);

      // Create the outline
      vtkSmartPointer<vtkOutlineFilter> outlineFilter =
        vtkSmartPointer<vtkOutlineFilter>::New();
      outlineFilter->SetInputData(data);

      vtkSmartPointer<vtkPolyDataMapper> outlineMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      outlineMapper->SetInputConnection(outlineFilter->GetOutputPort());
      vtkSmartPointer<vtkActor> outlineActor =
        vtkSmartPointer<vtkActor>::New();
      outlineActor->SetMapper(outlineMapper);
      outlineActor->GetProperty()->SetColor(colors->GetColor3d("Gray").GetData());
      outlineActor->GetProperty()->SetLineWidth(3);

      // 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(contourActor);
      renderer->AddActor(outlineActor);
      renderer->SetBackground(colors->GetColor3d("Burlywood").GetData());

      vtkSmartPointer<vtkSliderRepresentation3D> sliderRep =
        vtkSmartPointer<vtkSliderRepresentation3D>::New();
      sliderRep->SetMinimumValue(0.0);
      sliderRep->SetMaximumValue(30.0);
      sliderRep->SetValue(10.0);
      sliderRep->SetTitleText("Contour value");
      sliderRep->SetPoint1InWorldCoordinates(-20, -40, 0);
      sliderRep->SetPoint2InWorldCoordinates(0, -40, 0);
      sliderRep->SetSliderWidth(.2);
      sliderRep->SetLabelHeight(.1);

      vtkSmartPointer<vtkSliderWidget> sliderWidget =
        vtkSmartPointer<vtkSliderWidget>::New();
      sliderWidget->SetInteractor(interactor);
      sliderWidget->SetRepresentation(sliderRep);
      sliderWidget->SetAnimationModeToAnimate();
      sliderWidget->EnabledOn();

      vtkSmartPointer<vtkSliderCallback> callback =
        vtkSmartPointer<vtkSliderCallback>::New();
      callback->ContourFilter = contourFilter;

      sliderWidget->AddObserver(vtkCommand::InteractionEvent,callback);

      vtkSmartPointer<vtkInteractorStyleUser> style =
        vtkSmartPointer<vtkInteractorStyleUser>::New();
      interactor->SetInteractorStyle(style);

      renderWindow->SetSize(500,500);
      renderWindow->Render();
      renderWindow->Render();
      interactor->Start();

      return EXIT_SUCCESS;
    }
    namespace
    {
    void CreateData(vtkImageData* data)
    {
      data->SetExtent(-25,25,-25,25,0,0);
      data->AllocateScalars(VTK_DOUBLE,1);
      int* extent = data->GetExtent();

      for (int y = extent[2]; y <= extent[3]; y++)
      {
        for (int x = extent[0]; x <= extent[1]; x++)
        {
          double* pixel = static_cast<double*>(data->GetScalarPointer(x,y,0));
          pixel[0] = sqrt(pow(x,2.0) + pow(y,2.0));
        }
      }

      vtkSmartPointer<vtkXMLImageDataWriter> writer =
        vtkSmartPointer<vtkXMLImageDataWriter>::New();
      writer->SetFileName("data.vti");
      writer->SetInputData(data);
      writer->Write();
    }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(IsoContours)

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

### Download and Build IsoContours

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

    cd IsoContours/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:

    ./IsoContours

WINDOWS USERS

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