# QuadraticHexahedronDemo

VTKExamples/Cxx/GeometricObjects/QuadraticHexahedronDemo

### Description

This example shows the effect of changing the chord length error for a vtkQuadraticHexahedron.

### Code

QuadraticHexahedronDemo.cxx

    #include <vtkSmartPointer.h>

    #include <vtkUnstructuredGrid.h>
    #include <vtkQuadraticHexahedron.h>
    #include <vtkTessellatorFilter.h>
    #include <vtkNamedColors.h>

    #include <vtkSphereSource.h>
    #include <vtkGlyph3D.h>
    #include <vtkPoints.h>
    #include <vtkCellIterator.h>
    #include <vtkGenericCell.h>

    #include <vtkDataSetMapper.h>
    #include <vtkActor.h>
    #include <vtkProperty.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>

    #include <vtkTextProperty.h>
    #include <vtkTextMapper.h>
    #include <vtkActor2D.h>

    #include <vtkCommand.h>
    #include <vtkSliderWidget.h>
    #include <vtkSliderRepresentation2D.h>

    #include <vtkMath.h>
    #include <map>
    #include <sstream>

    namespace
    {
    static vtkSmartPointer<vtkUnstructuredGrid> MakeQuadraticHexahedron();
    void MakeWidget(vtkSmartPointer<vtkSliderWidget> &,
                    vtkSmartPointer<vtkTessellatorFilter> &,
                    vtkSmartPointer<vtkTextMapper> &,
                    vtkSmartPointer<vtkRenderWindowInteractor> &);
    }

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

      vtkSmartPointer<vtkUnstructuredGrid> uGrid =
        MakeQuadraticHexahedron();

      vtkSmartPointer<vtkTessellatorFilter> tessellate =
        vtkSmartPointer<vtkTessellatorFilter>::New();
      tessellate->SetInputData(uGrid);
      tessellate->SetChordError(.035);
      tessellate->Update();

      typedef std::map<const char *,int> CellContainer;
      CellContainer cellMap;

      int numTets = 0;
      vtkSmartPointer<vtkGenericCell> cell =
        vtkSmartPointer<vtkGenericCell>::New();
      vtkCellIterator *it = tessellate->GetOutput()->NewCellIterator();
      for (it->InitTraversal();
           !it->IsDoneWithTraversal();
           it->GoToNextCell())
      {
        it->GetCell(cell);
        cellMap[cell->GetRepresentativeCell()->GetClassName()]++;
        ++numTets;
      }
      it->Delete();

      vtkSmartPointer<vtkDataSetMapper> mapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      mapper->SetInputConnection(tessellate->GetOutputPort());
      mapper->ScalarVisibilityOff();

      // Create an actor for the grid
      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);
      actor->GetProperty()->SetDiffuseColor(
        namedColors->GetColor3d("Tomato").GetData());
      actor->GetProperty()->SetEdgeColor(
        namedColors->GetColor3d("IvoryBlack").GetData());
      actor->GetProperty()->EdgeVisibilityOn();

      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetRadius(.02);

      vtkSmartPointer<vtkGlyph3D> glyph3D =
        vtkSmartPointer<vtkGlyph3D>::New();
      glyph3D->SetInputData(uGrid);
      glyph3D->SetSourceConnection(sphereSource->GetOutputPort());
      glyph3D->ScalingOff();
      glyph3D->Update();

      vtkSmartPointer<vtkDataSetMapper> glyph3DMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      glyph3DMapper->SetInputConnection(glyph3D->GetOutputPort());
      glyph3DMapper->ScalarVisibilityOff();

      vtkSmartPointer<vtkActor> glyph3DActor =
        vtkSmartPointer<vtkActor>::New();
      glyph3DActor->SetMapper(glyph3DMapper);
      glyph3DActor->GetProperty()->SetColor(
        namedColors->GetColor3d("Banana").GetData());

      vtkSmartPointer<vtkTextProperty> textProperty =
        vtkSmartPointer<vtkTextProperty>::New();
      textProperty->SetFontSize(16);

      std::stringstream ss;
      ss << "# of Tetras: " << numTets << std::endl;
      vtkSmartPointer<vtkTextMapper> textMapper =
        vtkSmartPointer<vtkTextMapper>::New();
      textMapper->SetInput(ss.str().c_str());
      textMapper->SetTextProperty(textProperty);

      vtkSmartPointer<vtkActor2D> textActor =
        vtkSmartPointer<vtkActor2D>::New();
      textActor->SetMapper(textMapper);
      textActor->SetPosition(10, 250);

      // Visualize
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      renderWindow->SetSize(640, 512);
      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);

      vtkSmartPointer<vtkSliderWidget> widget =
        vtkSmartPointer<vtkSliderWidget>::New();
      MakeWidget(widget, tessellate, textMapper, interactor);

      renderer->AddActor(actor);
      renderer->AddActor(glyph3DActor);
      renderer->AddViewProp(textActor);
      renderer->SetBackground(namedColors->GetColor3d("SlateGray").GetData());

      renderWindow->Render();

      interactor->Start();

      return EXIT_SUCCESS;
    }

    namespace
    {
    // These callbacks do the actual work.
    // Callbacks for the interactions
    class SliderCallbackChordError : public vtkCommand
    {
    public:
      static SliderCallbackChordError *New()
      {
        return new SliderCallbackChordError;
      }
      virtual void Execute(vtkObject *caller, unsigned long, void*)
      {
        vtkSliderWidget *sliderWidget =
          reinterpret_cast<vtkSliderWidget*>(caller);
        double value = static_cast<vtkSliderRepresentation2D *>(sliderWidget->GetRepresentation())->GetValue();
        this->Tessellator->SetChordError(value);
        this->Tessellator->SetMaximumNumberOfSubdivisions(4);
        this->Tessellator->Update();

        typedef std::map<const char *,int> CellContainer;
        CellContainer cellMap;

        int numTets = 0;
        vtkSmartPointer<vtkGenericCell> cell =
          vtkSmartPointer<vtkGenericCell>::New();
        vtkCellIterator *it = this->Tessellator->GetOutput()->NewCellIterator();
        for (it->InitTraversal();
             !it->IsDoneWithTraversal();
             it->GoToNextCell())
        {
          it->GetCell(cell);
          cellMap[cell->GetRepresentativeCell()->GetClassName()]++;
          ++numTets;
        }
        it->Delete();
        std::stringstream ss;
        ss << "# of Tetras: " << numTets << std::endl;
        TextMapper->SetInput(ss.str().c_str());

      }
      SliderCallbackChordError():Tessellator(0),TextMapper(0) {}
      vtkTessellatorFilter *Tessellator;
      vtkTextMapper *TextMapper;
    };

    void
    MakeWidget(vtkSmartPointer<vtkSliderWidget> &widget,
               vtkSmartPointer<vtkTessellatorFilter> &tessellate,
               vtkSmartPointer<vtkTextMapper> &textMapper,
               vtkSmartPointer<vtkRenderWindowInteractor> &interactor)
    {
      // Setup a slider widget for each varying parameter
      double tubeWidth(.004);
      double sliderLength(.004);
      double titleHeight(.02);
      double labelHeight(.02);

      vtkSmartPointer<vtkSliderRepresentation2D> sliderRepChordError =
        vtkSmartPointer<vtkSliderRepresentation2D>::New();

      sliderRepChordError->SetMinimumValue(0.0);
      sliderRepChordError->SetMaximumValue(.07);
      sliderRepChordError->SetValue(tessellate->GetChordError());
      sliderRepChordError->SetTitleText("Chord error");

      sliderRepChordError->GetPoint1Coordinate()->SetCoordinateSystemToNormalizedDisplay();
      sliderRepChordError->GetPoint1Coordinate()->SetValue(.1, .1);
      sliderRepChordError->GetPoint2Coordinate()->SetCoordinateSystemToNormalizedDisplay();
      sliderRepChordError->GetPoint2Coordinate()->SetValue(.9, .1);

      sliderRepChordError->SetTubeWidth(tubeWidth);
      sliderRepChordError->SetSliderLength(sliderLength);
      sliderRepChordError->SetTitleHeight(titleHeight);
      sliderRepChordError->SetLabelHeight(labelHeight);

      widget->SetInteractor(interactor);
      widget->SetRepresentation(sliderRepChordError);
      widget->SetAnimationModeToAnimate();
      widget->EnabledOn();

      vtkSmartPointer<SliderCallbackChordError> callbackChordError =
        vtkSmartPointer<SliderCallbackChordError>::New();
      callbackChordError->Tessellator = tessellate;
      callbackChordError->TextMapper = textMapper;

      widget->AddObserver(vtkCommand::InteractionEvent,callbackChordError);
    }

    vtkSmartPointer<vtkUnstructuredGrid> MakeQuadraticHexahedron()
    {
      vtkSmartPointer<vtkQuadraticHexahedron> aHexahedron =
        vtkSmartPointer<vtkQuadraticHexahedron>::New();
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();

      vtkMath::RandomSeed(5070); // for testing
      double *pcoords = aHexahedron->GetParametricCoords();
      points->SetNumberOfPoints(aHexahedron->GetNumberOfPoints());
      for (int i = 0; i < aHexahedron->GetNumberOfPoints(); ++i)
      {
        aHexahedron->GetPointIds()->SetId(i, i);
        points->SetPoint(i,
                         *(pcoords + 3 * i) + vtkMath::Random(-.1,.1),
                         *(pcoords + 3 * i + 1) + vtkMath::Random(-.1,.1),
                         *(pcoords + 3 * i + 2) + vtkMath::Random(-.1,.1));
      }
      // Add the points and hexahedron to an unstructured grid
      vtkSmartPointer<vtkUnstructuredGrid> uGrid =
        vtkSmartPointer<vtkUnstructuredGrid>::New();
      uGrid->SetPoints(points);
      uGrid->InsertNextCell(aHexahedron->GetCellType(), aHexahedron->GetPointIds());

      return uGrid;
    }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(QuadraticHexahedronDemo)

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

    add_executable(QuadraticHexahedronDemo MACOSX_BUNDLE QuadraticHexahedronDemo.cxx )

    target_link_libraries(QuadraticHexahedronDemo ${VTK_LIBRARIES})

### Download and Build QuadraticHexahedronDemo

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

    cd QuadraticHexahedronDemo/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:

    ./QuadraticHexahedronDemo

WINDOWS USERS

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