# GeometryFilter

VTKExamples/Cxx/PolyData/GeometryFilter

### Description

This example demonstrates how to convert an unstructured grid to a polydata. Currently nothing is done with the resulting polydata. If someone has a good data set that demonstrates the conversion, please let us know.

### Code

GeometryFilter.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPolyData.h>
    #include <vtkUnstructuredGrid.h>
    #include <vtkCellArray.h>
    #include <vtkGeometryFilter.h>
    #include <vtkPointSource.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkUnstructuredGrid> unstructuredGrid =
        vtkSmartPointer<vtkUnstructuredGrid>::New();

      vtkSmartPointer<vtkGeometryFilter> geometryFilter =
        vtkSmartPointer<vtkGeometryFilter>::New();
      geometryFilter->SetInputData(unstructuredGrid);
      geometryFilter->Update();

      vtkPolyData* polydata = geometryFilter->GetOutput();

      std::cout << "Output has " << polydata->GetNumberOfPoints() << " points." << std::endl;

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(GeometryFilter)

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

### Download and Build GeometryFilter

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

    cd GeometryFilter/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:

    ./GeometryFilter

WINDOWS USERS

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