# 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.

For alpha != 0 (right window), the tetra are yellow, the lines are blue and the triangles are red.

The example requires a .vtp file and an optional alpha.

Seealso

See Delaunay3DDemo to interactively adjust Alpha.

Note

This original source code for this example is here.###Code

Delaunay3D.cxx

    #include <vtkDelaunay3D.h>
    #include <vtkSmartPointer.h>

    #include <vtkCellArray.h>
    #include <vtkProperty.h>
    #include <vtkDataSetMapper.h>
    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkPoints.h>
    #include <vtkPolyData.h>
    #include <vtkPolygon.h>
    #include <vtkMath.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkCleanPolyData.h>
    #include <vtkUnstructuredGrid.h>
    #include <vtkCellIterator.h>
    #include <vtkCellData.h>
    #include <vtkUnsignedCharArray.h>
    #include <vtkNamedColors.h>

    #include <vtkTextProperty.h>
    #include <vtkTextMapper.h>
    #include <vtkActor2D.h>

    #include <vtkXMLPolyDataReader.h>

    #include <sstream>

    int main ( int argc, char *argv[] )
    {
      float alpha = .5;
      if(argc < 2)
      {
        std::cout << "Usage: " << argv[0]
                  << " filename.vtp [alpha]" << std::endl;
        return EXIT_FAILURE;
      }
      if (argc > 2)
      {
        alpha = atof(argv[2]);
      }
      //Read the file
      vtkSmartPointer<vtkXMLPolyDataReader> reader =
        vtkSmartPointer<vtkXMLPolyDataReader>::New();
      reader->SetFileName(argv[1]);

      vtkSmartPointer<vtkNamedColors> color =
        vtkSmartPointer<vtkNamedColors>::New();

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

      vtkSmartPointer<vtkActor> originalActor =
        vtkSmartPointer<vtkActor>::New();
      originalActor->SetMapper(originalMapper);
      originalActor->GetProperty()->SetColor(color->GetColor3d("tomato").GetData());
      originalActor->GetProperty()->SetInterpolationToFlat();

      // 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());
      delaunayMapper->SetScalarModeToUseCellData();

      vtkSmartPointer<vtkActor> delaunayActor =
        vtkSmartPointer<vtkActor>::New();
      delaunayActor->SetMapper(delaunayMapper);
      delaunayActor->GetProperty()->SetColor(color->GetColor3d("banana").GetData());
      delaunayActor->GetProperty()->SetInterpolationToFlat();

      // 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(alpha);
      delaunay3DAlpha->Update();
      std::cout << "Alpha: " << alpha << std::endl;

      vtkSmartPointer<vtkUnsignedCharArray> cellData =
        vtkSmartPointer<vtkUnsignedCharArray>::New();
      cellData->SetNumberOfComponents(3);

      int numTetras = 0;
      int numLines = 0;
      int numTris = 0;
      int numVerts = 0;

      vtkSmartPointer<vtkCellIterator> it =
        delaunay3DAlpha->GetOutput()->NewCellIterator();
      for (it->InitTraversal(); !it->IsDoneWithTraversal(); it->GoToNextCell())
      {
        if (it->GetCellType() == VTK_TETRA)
        {
          numTetras++;
          cellData->InsertNextTypedTuple(color->GetColor3ub("Banana").GetData());
        }
        else if (it->GetCellType() == VTK_LINE)
        {
          numLines++;
          cellData->InsertNextTypedTuple(color->GetColor3ub("Peacock").GetData());
        }
        else if (it->GetCellType() == VTK_TRIANGLE)
        {
          numTris++;
          cellData->InsertNextTypedTuple(color->GetColor3ub("Tomato").GetData());
        }
        else if (it->GetCellType() == VTK_VERTEX)
        {
          numVerts++;
          cellData->InsertNextTypedTuple(color->GetColor3ub("Lime").GetData());
        }
      }

      std::stringstream ss;
      ss << "numTetras: " << numTetras << std::endl;
      ss << "numLines: " << numLines << std::endl;
      ss << "numTris: " << numTris << std::endl;
      ss << "numVerts: " << numVerts;

      // Set the cell color depending on cell type
      delaunay3DAlpha->GetOutput()->GetCellData()->SetScalars(cellData);

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

      vtkSmartPointer<vtkActor> delaunayAlphaActor =
        vtkSmartPointer<vtkActor>::New();
      delaunayAlphaActor->SetMapper(delaunayAlphaMapper);
      delaunayAlphaActor->GetProperty()->SetPointSize(5.0);
      delaunayAlphaActor->GetProperty()->SetInterpolationToFlat();

      // Visualize

      vtkSmartPointer<vtkTextProperty> textProperty =
        vtkSmartPointer<vtkTextProperty>::New();
      textProperty->SetFontSize(16);
      textProperty->SetColor(color->GetColor3d("Black").GetData());

      vtkSmartPointer<vtkTextMapper> textMapper =
        vtkSmartPointer<vtkTextMapper>::New();
      textMapper->SetInput(ss.str().c_str());
      textMapper->SetTextProperty(textProperty);

      vtkSmartPointer<vtkActor2D> textActor =
        vtkSmartPointer<vtkActor2D>::New();
      textActor->SetMapper(textMapper);
      textActor->SetPosition(10, 10);

      // 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};

      // Shared camera
      vtkSmartPointer<vtkCamera> sharedCamera =
        vtkSmartPointer<vtkCamera>::New();

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

      vtkSmartPointer<vtkRenderer> delaunayRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      delaunayRenderer->SetActiveCamera(sharedCamera);

      vtkSmartPointer<vtkRenderer> delaunayAlphaRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      delaunayAlphaRenderer->SetActiveCamera(sharedCamera);

      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);
      delaunayAlphaRenderer->AddViewProp(textActor);

      originalRenderer->SetBackground(
        color->GetColor3d("Slate_Grey").GetData());
      delaunayRenderer->SetBackground(
        color->GetColor3d("Light_Grey").GetData());
      delaunayAlphaRenderer->SetBackground(
        color->GetColor3d("Grey").GetData());

      originalRenderer->ResetCamera();
      renderWindow->Render();

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

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(Delaunay3D)

    find_package(VTK COMPONENTS
      vtkCommonColor
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersCore
      vtkIOXML
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping Delaunay3D: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(Delaunay3D MACOSX_BUNDLE Delaunay3D.cxx )
      target_link_libraries(Delaunay3D PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(Delaunay3D MACOSX_BUNDLE Delaunay3D.cxx )
      target_link_libraries(Delaunay3D PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS Delaunay3D
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### 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

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