# GraphToPolyData

VTKExamples/Cxx/Graphs/GraphToPolyData

### Description

This example creates a simple graph and then converts it to a polydata for visualization using Paraview.

Other Languages

See (Python)

### Code

GraphToPolyData.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPoints.h>
    #include <vtkMutableUndirectedGraph.h>
    #include <vtkGraphToPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

    int main(int, char *[])
    {
      // Create a graph
      vtkSmartPointer<vtkMutableUndirectedGraph> g =
        vtkSmartPointer<vtkMutableUndirectedGraph>::New();

      // Add 4 vertices to the graph
      vtkIdType v1 = g->AddVertex();
      vtkIdType v2 = g->AddVertex();
      vtkIdType v3 = g->AddVertex();
      vtkIdType v4 = g->AddVertex();

      // Add 3 edges to the graph
      g->AddEdge ( v1, v2 );
      g->AddEdge ( v1, v3 );
      g->AddEdge ( v1, v4 );

      // Create 4 points - one for each vertex
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      points->InsertNextPoint(0.0, 0.0, 0.0);
      points->InsertNextPoint(1.0, 0.0, 0.0);
      points->InsertNextPoint(0.0, 1.0, 0.0);
      points->InsertNextPoint(0.0, 0.0, 1.0);

      // Add the coordinates of the points to the graph
      g->SetPoints(points);

      // Convert the graph to a polydata
      vtkSmartPointer<vtkGraphToPolyData> graphToPolyData =
          vtkSmartPointer<vtkGraphToPolyData>::New();
      graphToPolyData->SetInput(g);
      graphToPolyData->Update();

      // Create a mapper and actor
      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(graphToPolyData->GetOutputPort());

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      // Create a renderer, render window, and 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 actor to the scene
      renderer->AddActor(actor);
      renderer->SetBackground(.3, .6, .3); // Background color green

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(GraphToPolyData)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersSources
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping GraphToPolyData: ${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(GraphToPolyData MACOSX_BUNDLE GraphToPolyData.cxx )
      target_link_libraries(GraphToPolyData PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(GraphToPolyData MACOSX_BUNDLE GraphToPolyData.cxx )
      target_link_libraries(GraphToPolyData PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS GraphToPolyData
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build GraphToPolyData

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

    cd GraphToPolyData/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:

    ./GraphToPolyData

WINDOWS USERS

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