# Hexahedron

VTKExamples/Cxx/GeometricObjects/Hexahedron

### Description

The hexahedron is a primary three-dimensional cell consisting of six quadrilateral faces, twelve edges, and eight vertices. The hexahedron is defined by an ordered list of eight points. The faces and edges must not intersect any other faces and edges, and the hexahedron must be convex.

### Code

Hexahedron.cxx

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkCellArray.h>
    #include <vtkDataSetMapper.h>
    #include <vtkHexahedron.h>
    #include <vtkNamedColors.h>
    #include <vtkPoints.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkSmartPointer.h>
    #include <vtkUnstructuredGrid.h>
    #include <vtkVersion.h>

    #include <algorithm>
    #include <array>
    #include <vector>

    int main(int, char* [])
    {

      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      // Set the background color.
      auto SetColor = [&colors](std::array<double, 3>& v,
                                std::string const& colorName) {
        auto const scaleFactor = 256.0;
        std::transform(std::begin(v), std::end(v), std::begin(v),
                       [=](double const& n) { return n / scaleFactor; });
        colors->SetColor(colorName, v.data());
        return;
      };
      std::array<double, 3> bkg{{51, 77, 102}};
      // std::array<double, 3> bkg{{26, 51, 77}};
      SetColor(bkg, "BkgColor");

      // For the hexahedron; setup the coordinates of eight points.
      // The two faces must be in counter clockwise order as viewed from the
      // outside.
      std::vector<std::array<double, 3>> pointCoordinates;
      pointCoordinates.push_back({{0.0, 0.0, 0.0}}); // Face 1
      pointCoordinates.push_back({{1.0, 0.0, 0.0}});
      pointCoordinates.push_back({{1.0, 1.0, 0.0}});
      pointCoordinates.push_back({{0.0, 1.0, 0.0}});
      pointCoordinates.push_back({{0.0, 0.0, 1.0}}); // Face 2
      pointCoordinates.push_back({{1.0, 0.0, 1.0}});
      pointCoordinates.push_back({{1.0, 1.0, 1.0}});
      pointCoordinates.push_back({{0.0, 1.0, 1.0}});

      // Create the points.
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();

      // Create a hexahedron from the points.
      vtkSmartPointer<vtkHexahedron> hex =
        vtkSmartPointer<vtkHexahedron>::New();

      for (auto i = 0; i < pointCoordinates.size(); ++i)
      {
        points->InsertNextPoint(pointCoordinates[i].data());
        hex->GetPointIds()->SetId(i, i);
      }

      // Add the hexahedron to a cell array.
      vtkSmartPointer<vtkCellArray> hexs =
        vtkSmartPointer<vtkCellArray>::New();
      hexs->InsertNextCell(hex);

      // Add the points and hexahedron to an unstructured grid.
      vtkSmartPointer<vtkUnstructuredGrid> uGrid =
        vtkSmartPointer<vtkUnstructuredGrid>::New();
      uGrid->SetPoints(points);
      uGrid->InsertNextCell(hex->GetCellType(), hex->GetPointIds());

      // Visualize.
      vtkSmartPointer<vtkDataSetMapper> mapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
    #if VTK_MAJOR_VERSION <= 5
      mapper->SetInputConnection(uGrid->GetProducerPort());
    #else
      mapper->SetInputData(uGrid);
    #endif

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->GetProperty()->SetColor(colors->GetColor3d("Cornsilk").GetData());
      actor->SetMapper(mapper);

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetWindowName("Hexahedron");
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      renderer->AddActor(actor);
      renderer->SetBackground(colors->GetColor3d("BkgColor").GetData());
      renderer->ResetCamera();
      renderer->GetActiveCamera()->Azimuth(30);
      renderer->GetActiveCamera()->Elevation(30);

      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(Hexahedron)

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

    add_executable(Hexahedron MACOSX_BUNDLE Hexahedron.cxx )

    target_link_libraries(Hexahedron ${VTK_LIBRARIES})

### Download and Build Hexahedron

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

    cd Hexahedron/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:

    ./Hexahedron

WINDOWS USERS

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