ExtractArrayComponent

#include <vtkArrayCalculator.h>
#include <vtkDoubleArray.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPolyData.h>

int main(int, char*[])
{
  vtkNew<vtkPoints> points;
  points->InsertNextPoint(1.0, 0.0, 0.0);
  points->InsertNextPoint(2.0, 0.0, 0.0);
  points->InsertNextPoint(3.0, 0.0, 0.0);

  vtkNew<vtkDoubleArray> array;
  array->SetName("InputArray");
  array->SetNumberOfComponents(3);
  array->InsertNextTuple3(1, 10, 100);
  array->InsertNextTuple3(2, 20, 200);
  array->InsertNextTuple3(3, 30, 300);

  vtkNew<vtkPolyData> polydata;
  polydata->SetPoints(points);
  polydata->GetPointData()->AddArray(array);

  vtkNew<vtkArrayCalculator> arrayCalculator;
  arrayCalculator->SetInputData(polydata);
  arrayCalculator->AddVectorArrayName("InputArray");
  arrayCalculator->SetFunction(
      "InputArray . jHat"); // Extract component '1' from the InputArray by
                            // taking the dot product of each tuple with the
                            // vector (0,1,0)
  arrayCalculator->SetResultArrayName("OutputArray");
  arrayCalculator->Update();

  vtkSmartPointer<vtkDoubleArray> outputArray = dynamic_cast<vtkDoubleArray*>(
      arrayCalculator->GetPolyDataOutput()->GetPointData()->GetArray(
          "OutputArray"));

  for (vtkIdType i = 0; i < outputArray->GetNumberOfTuples(); i++)
  {
    double val = outputArray->GetValue(i);
    std::cout << "output value " << i << ": " << val << std::endl;
  }

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ExtractArrayComponent)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  QUIET
)

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

cd ExtractArrayComponent/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./ExtractArrayComponent