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GetMiscPointData

vtk-examples/Cxx/PolyData/GetMiscPointData

Description

This example demonstrates how to get data stored at each point in a polydata.

Question

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

Code

GetMiscPointData.cxx

#include <string>
#include <vtkCellData.h>
#include <vtkDoubleArray.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPolyDataNormals.h>
#include <vtkXMLPolyDataReader.h>

int main(int argc, char* argv[])
{
  // Parse command line arguments
  if (argc != 3)
  {
    std::cout << "Required arguments: Filename ArrayName e.g. cowHead.vtp "
                 "Gauss_Curvature"
              << std::endl;
    return EXIT_FAILURE;
  }

  // Get filename from command line
  std::string filename = argv[1]; // first command line argument

  // Get array name
  std::string arrayName = argv[2]; // second command line argument

  // Read the file
  vtkNew<vtkXMLPolyDataReader> reader;
  std::cout << "Reading " << filename << std::endl;
  reader->SetFileName(filename.c_str());
  reader->Update();

  // Extract the polydata
  auto polydata = reader->GetOutput();

  // Get the number of points in the polydata
  vtkIdType idNumPointsInFile = polydata->GetNumberOfPoints();

  auto array = dynamic_cast<vtkDoubleArray*>(
      polydata->GetPointData()->GetArray(arrayName.c_str()));

  if (array)
  {
    std::cout << "Got array " << arrayName << " with " << idNumPointsInFile
              << " values" << std::endl;
    for (int i = 0; i < idNumPointsInFile; i++)
    {
      // Since there could be a lot of points just print the first 10
      if (i < 10 || i == idNumPointsInFile - 1)
      {
        double value;
        value = array->GetValue(i);
        std::cout << i << ": " << value << std::endl;
      }
      else
      {
        if (i == 10)
          std::cout << "..." << std::endl;
      }
    }
  }
  else
  {
    std::cout << "The file " << filename
              << " does not have a PointData array named " << arrayName
              << std::endl;
  }

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(GetMiscPointData)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkIOXML
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping GetMiscPointData: ${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(GetMiscPointData MACOSX_BUNDLE GetMiscPointData.cxx )
  target_link_libraries(GetMiscPointData PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(GetMiscPointData MACOSX_BUNDLE GetMiscPointData.cxx )
  target_link_libraries(GetMiscPointData PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS GetMiscPointData
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build GetMiscPointData

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

cd GetMiscPointData/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:

./GetMiscPointData

WINDOWS USERS

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