# EllipticalCylinderDemo

VTKExamples/Cxx/GeometricObjects/EllipticalCylinderDemo

### Description

The example shows the vtkPolyLine that forms the base of the elliptical cylinder and an oriented arrow that represents the vector that vtkLinearExtrusionFilter uses to create the cyliinder. The example takes an optional triple that defines the vector for the filter. The length of the vector is the height of the cylinder.

### Code

EllipticalCylinderDemo.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPolyLine.h>
    #include <vtkPoints.h>
    #include <vtkLinearExtrusionFilter.h>
    #include <vtkTubeFilter.h>
    #include <vtkArrowSource.h>
    #include <vtkTransform.h>
    #include <vtkTransformPolyDataFilter.h>

    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkProperty.h>
    #include <vtkCamera.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkInteractorStyleTrackballCamera.h>

    #include <vtkNamedColors.h>

    int main(int argc, char *argv[])
    {
      double nx = 0.0;
      double ny = 0.0;
      double nz = 100.0;

      if (argc > 3)
      {
        nx = atof(argv[1]);
        ny = atof(argv[2]);
        nz = atof(argv[3]);
      }
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      double angle = 0;
      double r1, r2;
      double centerX, centerY;
      r1 = 50;
      r2 = 30;
      centerX = 10.0;
      centerY = 5.0;

      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      int id = 0;
      while (angle <= 2.0 * vtkMath::Pi() + (vtkMath::Pi() / 60.0))
      {
        points->InsertNextPoint(r1 * cos(angle) + centerX,
                                r2 * sin(angle) + centerY,
                                0.0);
        angle = angle + (vtkMath::Pi() / 60.0);
        ++id;
      }

      vtkSmartPointer<vtkPolyLine> line =
        vtkSmartPointer<vtkPolyLine>::New();
      line->GetPointIds()->SetNumberOfIds(id);
      for(unsigned int i = 0; i < static_cast<unsigned int>(id); ++i)
      {
        line->GetPointIds()->SetId(i,i);
      }

      vtkSmartPointer<vtkCellArray> lines =
        vtkSmartPointer<vtkCellArray>::New();
      lines->InsertNextCell(line);

      vtkSmartPointer<vtkPolyData> polyData =
        vtkSmartPointer<vtkPolyData>::New();
      polyData->SetPoints(points);
      polyData->SetLines(lines);

      vtkSmartPointer<vtkLinearExtrusionFilter> extrude =
        vtkSmartPointer<vtkLinearExtrusionFilter>::New();
      extrude->SetInputData(polyData);
      extrude->SetExtrusionTypeToNormalExtrusion();
      extrude->SetVector(nx, ny, nz);
      extrude->Update();

      // Create an oriented arrow
      double startPoint[3], endPoint[3];
      startPoint[0] = centerX;
      startPoint[1] = centerY;
      startPoint[2] = 0.0;
      endPoint[0] = startPoint[0] + extrude->GetVector()[0];
      endPoint[1] = startPoint[1] + extrude->GetVector()[1];
      endPoint[2] = startPoint[2] + extrude->GetVector()[2];

      // Compute a basis
      double normalizedX[3];
      double normalizedY[3];
      double normalizedZ[3];

      // The X axis is a vector from start to end
      vtkMath::Subtract(endPoint, startPoint, normalizedX);
      double length = vtkMath::Norm(normalizedX);
      vtkMath::Normalize(normalizedX);

      // The Z axis is an arbitrary vector cross X
      double arbitrary[3];
      arbitrary[0] = vtkMath::Random(-10,10);
      arbitrary[1] = vtkMath::Random(-10,10);
      arbitrary[2] = vtkMath::Random(-10,10);
      vtkMath::Cross(normalizedX, arbitrary, normalizedZ);
      vtkMath::Normalize(normalizedZ);

      // The Y axis is Z cross X
      vtkMath::Cross(normalizedZ, normalizedX, normalizedY);
      vtkSmartPointer<vtkMatrix4x4> matrix =
        vtkSmartPointer<vtkMatrix4x4>::New();

      // Create the direction cosine matrix
      matrix->Identity();
      for (unsigned int i = 0; i < 3; i++)
      {
        matrix->SetElement(i, 0, normalizedX[i]);
        matrix->SetElement(i, 1, normalizedY[i]);
        matrix->SetElement(i, 2, normalizedZ[i]);
      }

      // Apply the transforms
      vtkSmartPointer<vtkTransform> transform =
        vtkSmartPointer<vtkTransform>::New();
      transform->Translate(startPoint);
      transform->Concatenate(matrix);
      transform->Scale(length, length, length);

      vtkSmartPointer<vtkArrowSource> arrowSource =
        vtkSmartPointer<vtkArrowSource>::New();
      arrowSource->SetTipResolution(31);
      arrowSource->SetShaftResolution(21);

      // Transform the polydata
      vtkSmartPointer<vtkTransformPolyDataFilter> transformPD =
        vtkSmartPointer<vtkTransformPolyDataFilter>::New();
      transformPD->SetTransform(transform);
      transformPD->SetInputConnection(arrowSource->GetOutputPort());

      //Create a mapper and actor for the arrow
      vtkSmartPointer<vtkPolyDataMapper> arrowMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      arrowMapper->SetInputConnection(transformPD->GetOutputPort());

      vtkSmartPointer<vtkActor> arrowActor =
        vtkSmartPointer<vtkActor>::New();
      arrowActor->SetMapper(arrowMapper);
      arrowActor->GetProperty()->SetColor(colors->GetColor3d("Tomato").GetData());

      vtkSmartPointer<vtkTubeFilter> tubes =
        vtkSmartPointer<vtkTubeFilter>::New();
      tubes->SetInputData(polyData);
      tubes->SetRadius(2.0);
      tubes->SetNumberOfSides(21);

      vtkSmartPointer<vtkPolyDataMapper> lineMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      lineMapper->SetInputConnection(tubes->GetOutputPort());

      vtkSmartPointer<vtkActor> lineActor =
        vtkSmartPointer<vtkActor>::New();
      lineActor->SetMapper(lineMapper);
      lineActor->GetProperty()->SetColor(colors->GetColor3d("Peacock").GetData());

      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(extrude->GetOutputPort());

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);
      actor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
      actor->GetProperty()->SetOpacity(.7);

      vtkSmartPointer<vtkRenderer> ren =
        vtkSmartPointer<vtkRenderer>::New();
      ren->SetBackground(colors->GetColor3d("Slate_grey").GetData());
      ren->AddActor(actor);
      ren->AddActor(lineActor);
      ren->AddActor(arrowActor);

      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(ren);
      renWin->SetSize(600, 600);

      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      vtkSmartPointer<vtkInteractorStyleTrackballCamera> style =
        vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New();
      iren->SetInteractorStyle(style);

      vtkSmartPointer<vtkCamera> camera =
        vtkSmartPointer<vtkCamera>::New();
      camera->SetPosition (0, 1, 0);
      camera->SetFocalPoint (0, 0, 0);
      camera->SetViewUp (0, 0, 1);
      camera->Azimuth(30);
      camera->Elevation(30);

      renWin->Render();

      ren->SetActiveCamera(camera);
      ren->ResetCamera();
      ren->ResetCameraClippingRange();
      iren->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(EllipticalCylinderDemo)

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

    add_executable(EllipticalCylinderDemo MACOSX_BUNDLE EllipticalCylinderDemo.cxx )

    target_link_libraries(EllipticalCylinderDemo ${VTK_LIBRARIES})

### Download and Build EllipticalCylinderDemo

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

    cd EllipticalCylinderDemo/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:

    ./EllipticalCylinderDemo

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.