# Delaunay2D

VTKExamples/Cxx/Filtering/Delaunay2D

### Description

This example generates a set of points aligned with an XY grid with random heights (z values). The Delaunay2D filter "magically" knows how to triangulate this type of point set because it projects the points by default onto the XY axis and then performs a 2D Delaunay triangulation. The result is a mesh on the input points.

### Code

Delaunay2D.cxx

    #include <vtkVersion.h>
    #include <vtkCellArray.h>
    #include <vtkPoints.h>
    #include <vtkTriangle.h>
    #include <vtkPolyData.h>
    #include <vtkPointData.h>
    #include <vtkLine.h>
    #include <vtkCellLocator.h>
    #include <vtkSmartPointer.h>
    #include <vtkDelaunay2D.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkProperty.h>
    #include <vtkVertexGlyphFilter.h>

    int main(int, char *[])
    {
      // Create a set of heighs on a grid.
      // This is often called a "terrain map".
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();

      unsigned int GridSize = 10;
      for(unsigned int x = 0; x < GridSize; x++)
      {
        for(unsigned int y = 0; y < GridSize; y++)
        {
            points->InsertNextPoint(x, y, (x+y)/(y+1));
        }
      }

      // Add the grid points to a polydata object
      vtkSmartPointer<vtkPolyData> polydata =
        vtkSmartPointer<vtkPolyData>::New();
      polydata->SetPoints(points);

      // Triangulate the grid points
      vtkSmartPointer<vtkDelaunay2D> delaunay =
      vtkSmartPointer<vtkDelaunay2D>::New();
    #if VTK_MAJOR_VERSION <= 5
      delaunay->SetInput(polydata);
    #else
      delaunay->SetInputData(polydata);
    #endif
      delaunay->Update();

      // Visualize
      vtkSmartPointer<vtkPolyDataMapper> meshMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      meshMapper->SetInputConnection(delaunay->GetOutputPort());

      vtkSmartPointer<vtkActor> meshActor =
        vtkSmartPointer<vtkActor>::New();
      meshActor->SetMapper(meshMapper);

      vtkSmartPointer<vtkVertexGlyphFilter> glyphFilter =
        vtkSmartPointer<vtkVertexGlyphFilter>::New();
    #if VTK_MAJOR_VERSION <= 5
      glyphFilter->SetInputConnection(polydata->GetProducerPort());
    #else
      glyphFilter->SetInputData(polydata);
    #endif
      glyphFilter->Update();

      vtkSmartPointer<vtkPolyDataMapper> pointMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      pointMapper->SetInputConnection(glyphFilter->GetOutputPort());

      vtkSmartPointer<vtkActor> pointActor =
        vtkSmartPointer<vtkActor>::New();
      pointActor->GetProperty()->SetColor(1,0,0);
      pointActor->GetProperty()->SetPointSize(3);
      pointActor->SetMapper(pointMapper);

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

      renderer->AddActor(meshActor);
      renderer->AddActor(pointActor);
      renderer->SetBackground(.3, .6, .3); // Background color green

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(Delaunay2D)

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

    add_executable(Delaunay2D MACOSX_BUNDLE Delaunay2D.cxx)

    target_link_libraries(Delaunay2D ${VTK_LIBRARIES})

### Download and Build Delaunay2D

Danger

The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.

Click here to download Delaunay2D and its CMakeLists.txt file. Once the tarball Delaunay2D.tar has been downloaded and extracted,

    cd Delaunay2D/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:

    ./Delaunay2D

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.