# OBBTreeExtractCells

VTKExamples/Cxx/DataStructures/OBBTreeExtractCells

### Code

OBBTreeExtractCells.cxx

    #include <vtkSmartPointer.h>
    #include <vtkSphereSource.h>
    #include <vtkPoints.h>
    #include <vtkIdList.h>
    #include <vtkPolyData.h>
    #include <vtkPointData.h>
    #include <vtkLine.h>
    #include <vtkLineSource.h>
    #include <vtkExtractCells.h>
    #include <vtkOBBTree.h>

    #include <vtkPolyDataMapper.h>
    #include <vtkDataSetMapper.h>
    #include <vtkActor.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetPhiResolution(7);
      sphereSource->SetThetaResolution(15);
      sphereSource->Update();

      // Create the locator
      vtkSmartPointer<vtkOBBTree> tree =
        vtkSmartPointer<vtkOBBTree>::New();
      tree->SetDataSet(sphereSource->GetOutput());
      tree->BuildLocator();

      // Intersect the locator with the line
      double lineP0[3] = {-0.6, -0.6, -0.6};
      double lineP1[3] = {.6, .6, .6};
      vtkSmartPointer<vtkPoints> intersectPoints =
        vtkSmartPointer<vtkPoints>::New();

      vtkSmartPointer<vtkIdList> intersectCells =
        vtkSmartPointer<vtkIdList>::New();

      double tol = 1.e-8;
      tree->SetTolerance(tol);
      tree->IntersectWithLine(lineP0, lineP1,
                              intersectPoints,
                              intersectCells);

      std::cout << "NumPoints: " << intersectPoints->GetNumberOfPoints()
                << std::endl;

      // Display list of intersections
      double intersection[3];
      for(int i = 0; i < intersectPoints->GetNumberOfPoints(); i++ )
      {
        intersectPoints->GetPoint(i, intersection);
        std::cout << "\tPoint Intersection " << i << ": "
                  << intersection[0] << ", "
                  << intersection[1] << ", "
                  << intersection[2] << std::endl;
      }

      std::cout << "NumCells: " << intersectCells->GetNumberOfIds()
                << std::endl;

      vtkIdType cellId;
      for(int i = 0; i < intersectCells->GetNumberOfIds(); i++ )
      {
        cellId = intersectCells->GetId(i);
        std::cout << "\tCellId " << i << ": "
                  << cellId << std::endl;
      }

      // Render the line, sphere and intersected cells
      vtkSmartPointer<vtkLineSource> lineSource =
        vtkSmartPointer<vtkLineSource>::New();
      lineSource->SetPoint1(lineP0);
      lineSource->SetPoint2(lineP1);

      vtkSmartPointer<vtkPolyDataMapper> lineMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      lineMapper->SetInputConnection(lineSource->GetOutputPort());
      vtkSmartPointer<vtkActor> lineActor =
        vtkSmartPointer<vtkActor>::New();
      lineActor->SetMapper(lineMapper);

      vtkSmartPointer<vtkPolyDataMapper> sphereMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      sphereMapper->SetInputConnection(sphereSource->GetOutputPort());
      vtkSmartPointer<vtkActor> sphereActor =
        vtkSmartPointer<vtkActor>::New();
      sphereActor->SetMapper(sphereMapper);
      sphereActor->GetProperty()->SetRepresentationToWireframe();
      sphereActor->GetProperty()->SetColor(0.89,0.81,0.34);

      vtkSmartPointer<vtkExtractCells> cellSource =
        vtkSmartPointer<vtkExtractCells>::New();
      cellSource->SetInputConnection(sphereSource->GetOutputPort());
      cellSource->SetCellList(intersectCells);

      vtkSmartPointer<vtkDataSetMapper> cellMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      cellMapper->SetInputConnection(cellSource->GetOutputPort());
      vtkSmartPointer<vtkActor> cellActor =
        vtkSmartPointer<vtkActor>::New();
      cellActor->SetMapper(cellMapper);
      cellActor->GetProperty()->SetColor(1.0, 0.3882, 0.2784);

      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(lineActor);
      renderer->AddActor(sphereActor);
      renderer->AddActor(cellActor);

      renderer->SetBackground(.4, .5, .6);
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(OBBTreeExtractCells)

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

### Download and Build OBBTreeExtractCells

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

    cd OBBTreeExtractCells/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:

    ./OBBTreeExtractCells

WINDOWS USERS

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