GetCellCenter

VTKExamples/Cxx/ImageData/GetCellCenter

Description

Unfortunately this function is not built in directly, but rather quite convoluted to call. This is an easy to use wrapper.

Code

GetCellCenter.cxx

#include <vtkSmartPointer.h>
#include <vtkCell.h>
#include <vtkImageData.h>

static void GetCellCenter(vtkImageData* imageData, const unsigned int cellId,
                          double center[3]);

int main(int, char *[])
{
  // Create an image data
  vtkSmartPointer<vtkImageData> imageData = vtkSmartPointer<vtkImageData>::New();

  // Specify the size of the image data
  imageData->SetDimensions(3,3,2); // This will cause 18 points and 4 cells
  imageData->SetSpacing(1.0, 1.0, 1.0);
  imageData->SetOrigin(0.0, 0.0, 0.0);

  std::cout << "Number of points: " << imageData->GetNumberOfPoints() << std::endl;
  std::cout << "Number of cells: " << imageData->GetNumberOfCells() << std::endl;

  double center[3] = {0,0,0};
  for(vtkIdType cellId = 0; cellId < imageData->GetNumberOfCells(); ++cellId)
  {
    GetCellCenter(imageData, cellId, center);

    std::cout << "Cell " << cellId << " center: " << center[0] << " "
              << center[1] << " " << center[2] << std::endl;
  }

  return EXIT_SUCCESS;
}

void GetCellCenter(vtkImageData* imageData, const unsigned int cellId, double center[3])
{
  double pcoords[3] = {0,0,0};
  double *weights = new double [imageData->GetMaxCellSize()];
  vtkCell* cell = imageData->GetCell(cellId);
  int subId = cell->GetParametricCenter(pcoords);
  cell->EvaluateLocation(subId, pcoords, center, weights);
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(GetCellCenter)

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

Download and Build GetCellCenter

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

cd GetCellCenter/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:

./GetCellCenter

WINDOWS USERS

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