# Delaunay3D

VTKExamples/Cxx/Modelling/Delaunay3D

### Description

This example creates a tetrahedral mesh from unorganized points. The example uses the vtkDelaunay3D filter. The resulting mesh will be a solid convex hull of the original points. The example takes the points from a XML PolyData file (.vtp) produces the 3D Delaunay tetrahedralization (both with alpha = 0 and a non-zero alpha), and displays the result on the screen.

### Code

Delaunay3D.cxx

    #include <vtkCellArray.h>
    #include <vtkProperty.h>
    #include <vtkDataSetMapper.h>
    #include <vtkActor.h>
    #include <vtkPoints.h>
    #include <vtkPolyData.h>
    #include <vtkPolygon.h>
    #include <vtkSmartPointer.h>
    #include <vtkMath.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkCleanPolyData.h>
    #include <vtkDelaunay3D.h>
    #include <vtkXMLPolyDataReader.h>

    int main ( int argc, char *argv[] )
    {
      if(argc < 2)
      {
        std::cout << "Usage: " << argv[0]
                  << " filename.vtp" << std::endl;
        return EXIT_FAILURE;
      }

      //Read the file
      vtkSmartPointer<vtkXMLPolyDataReader> reader =
        vtkSmartPointer<vtkXMLPolyDataReader>::New();
      reader->SetFileName(argv[1]);

      vtkSmartPointer<vtkDataSetMapper> originalMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      originalMapper->SetInputConnection(reader->GetOutputPort());

      vtkSmartPointer<vtkActor> originalActor =
        vtkSmartPointer<vtkActor>::New();
      originalActor->SetMapper(originalMapper);
      originalActor->GetProperty()->SetColor(1,0,0);

      // Clean the polydata. This will remove duplicate points that may be
      // present in the input data.
      vtkSmartPointer<vtkCleanPolyData> cleaner =
        vtkSmartPointer<vtkCleanPolyData>::New();
      cleaner->SetInputConnection (reader->GetOutputPort());

      // Generate a tetrahedral mesh from the input points. By
      // default, the generated volume is the convex hull of the points.
      vtkSmartPointer<vtkDelaunay3D> delaunay3D =
        vtkSmartPointer<vtkDelaunay3D>::New();
      delaunay3D->SetInputConnection (cleaner->GetOutputPort());

      vtkSmartPointer<vtkDataSetMapper> delaunayMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      delaunayMapper->SetInputConnection(delaunay3D->GetOutputPort());

      vtkSmartPointer<vtkActor> delaunayActor =
        vtkSmartPointer<vtkActor>::New();
      delaunayActor->SetMapper(delaunayMapper);
      delaunayActor->GetProperty()->SetColor(1,0,0);

      // Generate a mesh from the input points. If Alpha is non-zero, then
      // tetrahedra, triangles, edges and vertices that lie within the
      // alpha radius are output.
      vtkSmartPointer<vtkDelaunay3D> delaunay3DAlpha =
        vtkSmartPointer<vtkDelaunay3D>::New();
      delaunay3DAlpha->SetInputConnection (cleaner->GetOutputPort());
      delaunay3DAlpha->SetAlpha(0.1);

      vtkSmartPointer<vtkDataSetMapper> delaunayAlphaMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      delaunayAlphaMapper->SetInputConnection(delaunay3DAlpha->GetOutputPort());

      vtkSmartPointer<vtkActor> delaunayAlphaActor =
        vtkSmartPointer<vtkActor>::New();
      delaunayAlphaActor->SetMapper(delaunayAlphaMapper);
      delaunayAlphaActor->GetProperty()->SetColor(1,0,0);

      // Visualize

      // Define viewport ranges
      // (xmin, ymin, xmax, ymax)
      double leftViewport[4] = {0.0, 0.0, 0.33, 1.0};
      double centerViewport[4] = {0.33, 0.0, 0.66, 1.0};
      double rightViewport[4] = {0.66, 0.0, 1.0, 1.0};

      // Create a renderer, render window, and interactor
      vtkSmartPointer<vtkRenderer> originalRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderer> delaunayRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderer> delaunayAlphaRenderer =
        vtkSmartPointer<vtkRenderer>::New();

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(900,300);

      renderWindow->AddRenderer(originalRenderer);
      originalRenderer->SetViewport(leftViewport);
      renderWindow->AddRenderer(delaunayRenderer);
      delaunayRenderer->SetViewport(centerViewport);
      renderWindow->AddRenderer(delaunayAlphaRenderer);
      delaunayAlphaRenderer->SetViewport(rightViewport);

      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      originalRenderer->AddActor(originalActor);
      delaunayRenderer->AddActor(delaunayActor);
      delaunayAlphaRenderer->AddActor(delaunayAlphaActor);

      originalRenderer->SetBackground(.3, .6, .3);
      delaunayRenderer->SetBackground(.4, .6, .3);
      delaunayAlphaRenderer->SetBackground(.5, .6, .3);

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

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(Delaunay3D)

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

    add_executable(Delaunay3D MACOSX_BUNDLE Delaunay3D.cxx)

    target_link_libraries(Delaunay3D ${VTK_LIBRARIES})

### Download and Build Delaunay3D

Click here to download Delaunay3D and its CMakeLists.txt file. Once the tarball Delaunay3D.tar has been downloaded and extracted,

    cd Delaunay3D/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:

    ./Delaunay3D

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.