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GeometryFilter

vtk-examples/Cxx/PolyData/GeometryFilter

Description

This example demonstrates how to convert an unstructured grid to a polydata. Currently nothing is done with the resulting polydata.

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

GeometryFilter.cxx

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

namespace {
template <typename T>
vtkSmartPointer<vtkUnstructuredGrid> MakeUnstructuredGrid(vtkSmartPointer<T>);
}

int main(int argc, char* argv[])
{
  auto geometryFilter = vtkSmartPointer<vtkGeometryFilter>::New();
  if (argc < 2)
  {
    // std::cerr << "Usage: " << argv[0] << " Filename(.vtk) e.g. uGridEx.vtk "
    //          << std::endl;
    auto unstructuredGrid =
        MakeUnstructuredGrid(vtkSmartPointer<vtkVertex>::New());
    geometryFilter->SetInputData(unstructuredGrid);
  }
  else
  {
    // Create the reader for the data.
    // This is the data that will be rendered.
    std::string filename = argv[1];
    std::cout << "Loading " << filename.c_str() << std::endl;
    vtkNew<vtkUnstructuredGridReader> reader;
    reader->SetFileName(filename.c_str());
    geometryFilter->SetInputConnection(reader->GetOutputPort());
  }

  geometryFilter->Update();

  vtkPolyData* polydata = geometryFilter->GetOutput();

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

  return EXIT_SUCCESS;
}

namespace {
template <typename T>
vtkSmartPointer<vtkUnstructuredGrid>
MakeUnstructuredGrid(vtkSmartPointer<T> aCell)
{
  double* pcoords = aCell->GetParametricCoords();
  for (int i = 0; i < aCell->GetNumberOfPoints(); ++i)
  {
    aCell->GetPointIds()->SetId(i, i);
    aCell->GetPoints()->SetPoint(i, *(pcoords + 3 * i), *(pcoords + 3 * i + 1),
                                 *(pcoords + 3 * i + 2));
  }

  vtkNew<vtkUnstructuredGrid> ug;
  ug->SetPoints(aCell->GetPoints());
  ug->InsertNextCell(aCell->GetCellType(), aCell->GetPointIds());
  return ug;
}
} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(GeometryFilter)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersGeometry
  vtkFiltersSources
  vtkIOLegacy
  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.