# CellTreeLocator

VTKExamples/Cxx/PolyData/CellTreeLocator

### Code

CellTreeLocator.cxx

    #include <vtkPolyData.h>
    #include <vtkSphereSource.h>
    #include <vtkSmartPointer.h>
    #include <vtkUnstructuredGrid.h>
    #include <vtkCellTreeLocator.h>
    #include <vtkGenericCell.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetCenter(0.0, 0.0, 0.0);
      sphereSource->SetRadius(1.0);
      sphereSource->Update();

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

      double testInside[3] = {.5, 0.0, 0.0};
      double testOutside[3] = {10.0, 0.0, 0.0};

      double pcoords[3], weights[3];

      vtkIdType cellId;

      vtkSmartPointer<vtkGenericCell> cell = vtkSmartPointer<vtkGenericCell>::New();

      int returnValue = EXIT_SUCCESS;

      // Should be inside
      cellId = cellTree->FindCell(testInside,0,
                                  cell, pcoords, weights);
      if (cellId>=0)
      {
        std::cout << "First point: in cell " << cellId << std::endl;
      }
      else
      {
        std::cout << "ERROR: Cell was not found but should have been." << std::endl;
        returnValue = EXIT_FAILURE;
      }

      // Should be outside
      cellId = cellTree->FindCell(testOutside,0,
                                cell, pcoords, weights);
      if (cellId>=0)
      {
        std::cout << "ERROR: Found point in cell " << cellId
                  << " but it should be outside the domain." << std::endl;
        returnValue = EXIT_FAILURE;
      }
      else
      {
        std::cout << "Second point: outside" << std::endl;
      }

      return returnValue;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(CellTreeLocator)

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

### Download and Build CellTreeLocator

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

    cd CellTreeLocator/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:

    ./CellTreeLocator

WINDOWS USERS

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