# Triangle

VTKExamples/Cxx/GeometricObjects/Triangle

### Description

The triangle is a primary two-dimensional cell. The triangle is defined by a counterclockwise ordered list of three points. The order of the points specifies the direction of the surface normal using the right-hand rule.

### Code

Triangle.cxx

    #include <vtkVersion.h>
    #include <vtkSmartPointer.h>
    #include <vtkTriangle.h>
    #include <vtkCellArray.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

    int main(int , char *[])
    {
      // Create a triangle
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      points->InsertNextPoint ( 1.0, 0.0, 0.0 );
      points->InsertNextPoint ( 0.0, 0.0, 0.0 );
      points->InsertNextPoint ( 0.0, 1.0, 0.0 );

      vtkSmartPointer<vtkTriangle> triangle =
        vtkSmartPointer<vtkTriangle>::New();
      triangle->GetPointIds()->SetId ( 0, 0 );
      triangle->GetPointIds()->SetId ( 1, 1 );
      triangle->GetPointIds()->SetId ( 2, 2 );

      vtkSmartPointer<vtkCellArray> triangles =
        vtkSmartPointer<vtkCellArray>::New();
      triangles->InsertNextCell ( triangle );

      // Create a polydata object
      vtkSmartPointer<vtkPolyData> trianglePolyData =
        vtkSmartPointer<vtkPolyData>::New();

      // Add the geometry and topology to the polydata
      trianglePolyData->SetPoints ( points );
      trianglePolyData->SetPolys ( triangles );

      // Create mapper and actor
      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
    #if VTK_MAJOR_VERSION <= 5
      mapper->SetInput(trianglePolyData);
    #else
      mapper->SetInputData(trianglePolyData);
    #endif
      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      // Create a renderer, render window, and an interactor
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      // Add the actors to the scene
      renderer->AddActor(actor);
      renderer->SetBackground(.1, .2, .4); // Background color dark blue

      // Render and interact
      renderWindow->Render();
      renderWindowInteractor->Start();
      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(Triangle)

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

    add_executable(Triangle MACOSX_BUNDLE Triangle.cxx )

    target_link_libraries(Triangle ${VTK_LIBRARIES})

### Download and Build Triangle

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

    cd Triangle/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:

    ./Triangle

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.