# PolyLine1

VTKExamples/Cxx/GeometricObjects/PolyLine1

### Code

PolyLine1.cxx

    #include <vtkActor.h>
    #include <vtkCellArray.h>
    #include <vtkMath.h>
    #include <vtkNamedColors.h>
    #include <vtkPoints.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkSmartPointer.h>
    #include <vtkVersion.h>

    #include <algorithm>
    #include <array>
    #include <cmath>
    #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{{26, 51, 102}};
      SetColor(bkg, "BkgColor");

      // vtkPoints represents 3D points. The data model for vtkPoints is an array of
      // vx-vy-vz triplets accessible by (point or cell) id.
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      points->SetNumberOfPoints(6);
      double c = std::cos(vtkMath::Pi() / 6); // helper variable
      points->SetPoint(0, 0.0, -1.0, 0.0);
      points->SetPoint(1, c, -0.5, 0.0);
      points->SetPoint(2, c, 0.5, 0.0);
      points->SetPoint(3, 0.0, 1.0, 0.0);
      points->SetPoint(4, -c, 0.5, 0.0);
      points->SetPoint(5, -c, -0.5, 0.0);

      // vtkCellArray is a supporting object that explicitly represents cell
      // connectivity.
      // The cell array structure is a raw integer list of the form:
      // (n,id1,id2,...,idn, n,id1,id2,...,idn, ...) where n is the number of points
      // in
      // the cell, and id is a zero-offset index into an associated point list.
      vtkSmartPointer<vtkCellArray> lines =
        vtkSmartPointer<vtkCellArray>::New();
      lines->InsertNextCell(7);
      lines->InsertCellPoint(0);
      lines->InsertCellPoint(1);
      lines->InsertCellPoint(2);
      lines->InsertCellPoint(3);
      lines->InsertCellPoint(4);
      lines->InsertCellPoint(5);
      lines->InsertCellPoint(0);

      // vtkPolyData is a data object that is a concrete implementation of
      // vtkDataSet.
      // vtkPolyData represents a geometric structure consisting of vertices, lines,
      // polygons, and/or triangle strips
      vtkSmartPointer<vtkPolyData> polygon =
        vtkSmartPointer<vtkPolyData>::New();
      polygon->SetPoints(points);
      polygon->SetLines(lines);

      // vtkPolyDataMapper is a class that maps polygonal data (i.e., vtkPolyData)
      // to graphics primitives
      vtkSmartPointer<vtkPolyDataMapper> polygonMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      polygonMapper->SetInputData(polygon);
      polygonMapper->Update();

      // Create an actor to represent the polygon. The actor orchestrates rendering
      // of
      // the mapper's graphics primitives. An actor also refers to properties via a
      // vtkProperty instance, and includes an internal transformation matrix. We
      // set this actor's mapper to be polygonMapper which we created above.
      vtkSmartPointer<vtkActor> polygonActor =
        vtkSmartPointer<vtkActor>::New();
      polygonActor->SetMapper(polygonMapper);
      polygonActor->GetProperty()->SetColor(
        colors->GetColor3d("AliceBlue").GetData());

      // Create the Renderer and assign actors to it. A renderer is like a
      // viewport. It is part or all of a window on the screen and it is
      // responsible for drawing the actors it has.  We also set the
      // background color here.
      vtkSmartPointer<vtkRenderer> ren =
        vtkSmartPointer<vtkRenderer>::New();
      ren->AddActor(polygonActor);
      ren->SetBackground(colors->GetColor3d("BkgColor").GetData());

      // Automatically set up the camera based on the visible actors.
      // The camera will reposition itself to view the center point of the actors,
      // and move along its initial view plane normal
      // (i.e., vector defined from camera position to focal point) so that all of
      // the
      // actors can be seen.
      ren->ResetCamera();

      // Finally we create the render window which will show up on the screen
      // We put our renderer into the render window using AddRenderer. We
      // also set the size to be 300 pixels by 300.
      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->SetWindowName("OrderedPolyLine");
      renWin->AddRenderer(ren);
      renWin->SetSize(300, 300);

      // The vtkRenderWindowInteractor class watches for events (e.g., keypress,
      // mouse) in the vtkRenderWindow. These events are translated into
      // event invocations that VTK understands (see VTK/Common/vtkCommand.h
      // for all events that VTK processes). Then observers of these VTK
      // events can process them as appropriate.
      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);
      iren->Initialize();
      iren->Start();
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(PolyLine1)

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

    add_executable(PolyLine1 MACOSX_BUNDLE PolyLine1.cxx )

    target_link_libraries(PolyLine1 ${VTK_LIBRARIES})

### Download and Build PolyLine1

Click here to download PolyLine1 and its CMakeLists.txt file. Once the tarball PolyLine1.tar has been downloaded and extracted,

    cd PolyLine1/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:

    ./PolyLine1

WINDOWS USERS

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