VTK/Examples/Cxx/Utilities/ExtractArrayComponent

ExtractArrayComponent.cxx

#include <vtkVersion.h>
#include <vtkArrayCalculator.h>
#include <vtkDoubleArray.h>
#include <vtkPointData.h>
#include <vtkPolyData.h>
#include <vtkSmartPointer.h>

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

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

  vtkSmartPointer<vtkPolyData> polydata =
      vtkSmartPointer<vtkPolyData>::New();
  polydata->SetPoints(points);
  polydata->GetPointData()->AddArray(array);

  vtkSmartPointer<vtkArrayCalculator> arrayCalculator =
      vtkSmartPointer<vtkArrayCalculator>::New();
#if VTK_MAJOR_VERSION <= 5
  arrayCalculator->SetInput(polydata);
#else
  arrayCalculator->SetInputData(polydata);
#endif
  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 =
    vtkDoubleArray::SafeDownCast(
      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;
}

Please try the new VTKExamples website.

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)

PROJECT(ExtractArrayComponent)

find_package(VTK REQUIRED)
include(${VTK_USE_FILE})

add_executable(ExtractArrayComponent MACOSX_BUNDLE ExtractArrayComponent.cxx)

if(VTK_LIBRARIES)
  target_link_libraries(ExtractArrayComponent ${VTK_LIBRARIES})
else()
  target_link_libraries(ExtractArrayComponent vtkHybrid vtkWidgets)
endif()

Download and Build ExtractArrayComponent

Click here to download ExtractArrayComponent. and its CMakeLists.txt file.

Once the tarball ExtractArrayComponent.tar has been downloaded and extracted,

cd ExtractArrayComponent/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:

./ExtractArrayComponent

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