GetCellCenter

Description¶

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

Question

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

Code¶

GetCellCenter.cxx

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

namespace {

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

}

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

  // 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;
}

namespace {

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);
}

} // namespace

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(GetCellCenter)

find_package(VTK COMPONENTS 
  CommonCore
  CommonDataModel
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "GetCellCenter: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
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}
)

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.