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# MultiBlockDataSet

VTKEx/Cxx/CompositeData/MultiBlockDataSet

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See (Python)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

MultiBlockDataSet.cxx

    // Demonstrates how to make and use VTK's MultiBlock type data

    #include <vtkActor.h>
    #include <vtkCompositeDataGeometryFilter.h>
    #include <vtkExtractEdges.h>
    #include <vtkMultiBlockDataSet.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>
    #include <vtkSphereSource.h>

    int main (int, char *[])
    {
      // PART 1 Make some Data
      // make a tree
      vtkSmartPointer<vtkMultiBlockDataSet> root =
        vtkSmartPointer<vtkMultiBlockDataSet>::New();

      vtkSmartPointer<vtkMultiBlockDataSet> branch =
        vtkSmartPointer<vtkMultiBlockDataSet>::New();
      root->SetBlock(0, branch);

      // make some leaves
      vtkSmartPointer<vtkSphereSource> leaf1 =
        vtkSmartPointer<vtkSphereSource>::New();
      leaf1->SetCenter(0,0,0);
      leaf1->Update();
      branch->SetBlock(0, leaf1->GetOutput());

      vtkSmartPointer<vtkSphereSource> leaf2 =
        vtkSmartPointer<vtkSphereSource>::New();
      leaf2->SetCenter(1.75,2.5,0);
      leaf2->SetRadius(1.5);
      leaf2->Update();
      branch->SetBlock(1, leaf2->GetOutput());

      vtkSmartPointer<vtkSphereSource> leaf3 =
        vtkSmartPointer<vtkSphereSource>::New();
      leaf3->SetCenter(4,0,0);
      leaf3->SetRadius(2);
      leaf3->Update();
      root->SetBlock(1, leaf3->GetOutput());

      // uncomment to inspect
      //std::cerr << root->GetClassName() << std::endl;
      //root->PrintSelf(std::cerr, vtkIndent(0));

      // PART 2 Do something with the data
      // a non composite aware filter, the pipeline will iterate
      vtkSmartPointer<vtkExtractEdges> edges =
        vtkSmartPointer<vtkExtractEdges>::New();
      edges->SetInputData(root);

      // uncomment to inspect
      //edges->Update();
      //cerr << edges->GetOutputDataObject(0)->GetClassName() << endl;
      //edges->GetOutputDataObject(0)->PrintSelf(std::cerr, vtkIndent(0));

      // PART 3 Show the data
      // also demonstrate a composite aware filter
      // this filter aggregates all blocks into one polydata
      // this is handy for display, although fairly limited
      // see vtkCompositePolyDataMapper2 for something better
      vtkSmartPointer<vtkCompositeDataGeometryFilter> polydata =
        vtkSmartPointer<vtkCompositeDataGeometryFilter>::New();
      polydata->SetInputConnection(edges->GetOutputPort());

      // uncomment to inspect
      //polydata->Update();
      //std::cerr << polydata->GetOutput()->GetClassName() << std::endl;
      //polydata->GetOutput()->PrintSelf(std::cerr, vtkIndent(0));

      // display the data
      vtkSmartPointer<vtkRenderer> aren = vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renWin  =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(aren);
      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(0, polydata->GetOutputPort(0));

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

      renWin->Render();
      iren->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(MultiBlockDataSet)

    find_package(VTK COMPONENTS
      vtkvtkCommonCore
      vtkvtkCommonDataModel
      vtkvtkFiltersExtraction
      vtkvtkFiltersGeometry
      vtkvtkFiltersSources
      vtkvtkInteractionStyle
      vtkvtkRenderingContextOpenGL2
      vtkvtkRenderingCore
      vtkvtkRenderingFreeType
      vtkvtkRenderingGL2PSOpenGL2
      vtkvtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping MultiBlockDataSet: ${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(MultiBlockDataSet MACOSX_BUNDLE MultiBlockDataSet.cxx )
      target_link_libraries(MultiBlockDataSet PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(MultiBlockDataSet MACOSX_BUNDLE MultiBlockDataSet.cxx )
      target_link_libraries(MultiBlockDataSet PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS MultiBlockDataSet
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build MultiBlockDataSet

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

    cd MultiBlockDataSet/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:

    ./MultiBlockDataSet

WINDOWS USERS

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