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ArrayCalculator

vtk-examples/Cxx/Utilities/ArrayCalculator

Question

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

Code

ArrayCalculator.cxx

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

#include <iostream>
#include <string>

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("orig");
  array->InsertNextValue(1.0);
  array->InsertNextValue(2.0);
  array->InsertNextValue(3.0);

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

  vtkNew<vtkArrayCalculator> calc1;
  calc1->SetInputData(polydata);
  calc1->AddScalarArrayName("orig");
  calc1->SetFunction("orig+1");
  calc1->SetResultArrayName("orig");
  calc1->Update();

  auto output1 = dynamic_cast<vtkDoubleArray*>(
      calc1->GetPolyDataOutput()->GetPointData()->GetArray("orig"));

  for (vtkIdType i = 0; i < output1->GetNumberOfTuples(); i++)
  {
    double val = output1->GetValue(i);
    cout << "output1 value " << i << ": " << val << endl;
  }

  vtkNew<vtkArrayCalculator> calc2;
  calc2->SetInputData(polydata);
  calc2->AddScalarArrayName("orig");
  calc2->SetFunction("if(orig=2,1,orig)");
  calc2->SetResultArrayName("new");
  calc2->Update();

  auto output2 = dynamic_cast<vtkDoubleArray*>(
      calc2->GetPolyDataOutput()->GetPointData()->GetArray("new"));

  for (vtkIdType i = 0; i < output2->GetNumberOfTuples(); i++)
  {
    double val = output2->GetValue(i);
    cout << "output2 value " << i << ": " << val << endl;
  }

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ArrayCalculator)

find_package(VTK COMPONENTS 
  CommonCore
  CommonDataModel
  FiltersCore
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ArrayCalculator: 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(ArrayCalculator MACOSX_BUNDLE ArrayCalculator.cxx )
  target_link_libraries(ArrayCalculator PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ArrayCalculator
  MODULES ${VTK_LIBRARIES}
)

Download and Build ArrayCalculator

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

cd ArrayCalculator/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:

./ArrayCalculator

WINDOWS USERS

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