PolyDataAlgorithmReader

#include <vtkPolyData.h>
#include <vtkSmartPointer.h>

#include <vtkTestReader.h>

int main(int, char*[])
{
  vtkSmartPointer<vtkTestReader> reader = vtkSmartPointer<vtkTestReader>::New();
  reader->Update();

  vtkPolyData* polydata = reader->GetOutput();
  polydata->Print(std::cout);

  return EXIT_SUCCESS;
}

#ifndef __vtkTestReader_h
#define __vtkTestReader_h

#include <vtkPolyDataAlgorithm.h>

class vtkTestReader : public vtkPolyDataAlgorithm
{
public:
  vtkTypeMacro(vtkTestReader, vtkPolyDataAlgorithm);
  void PrintSelf(ostream& os, vtkIndent indent);

  static vtkTestReader* New();

protected:
  vtkTestReader();
  ~vtkTestReader();

  int FillOutputPortInformation(int port, vtkInformation* info);
  int RequestData(vtkInformation*, vtkInformationVector**,
                  vtkInformationVector*);

private:
  vtkTestReader(const vtkTestReader&);  // Not implemented.
  void operator=(const vtkTestReader&); // Not implemented.

  char* FileName;
};

#endif

#include <vtkTestReader.h>

#include <vtkDataObject.h>
#include <vtkInformation.h>
#include <vtkInformationVector.h>
#include <vtkNew.h>
#include <vtkObjectFactory.h>
#include <vtkStreamingDemandDrivenPipeline.h>

vtkStandardNewMacro(vtkTestReader);

vtkTestReader::vtkTestReader()
{
  this->FileName = NULL;
  this->SetNumberOfInputPorts(0);
  this->SetNumberOfOutputPorts(1);
}

vtkTestReader::~vtkTestReader()
{
}

// This override is not needed as the FillOutputPortInformation on
// vtkPolyDataAlgorithm does this.  Override this if you need something
// different from one output that is a vtkPolyData
int vtkTestReader::FillOutputPortInformation(int port, vtkInformation* info)
{
  if (port == 0)
  {
    info->Set(vtkDataObject::DATA_TYPE_NAME(), "vtkPolyData");

    return 1;
  }

  return 0;
}

int vtkTestReader::RequestData(vtkInformation* vtkNotUsed(request),
                               vtkInformationVector** vtkNotUsed(inputVector),
                               vtkInformationVector* outputVector)
{

  // Get the output
  vtkPolyData* output = vtkPolyData::GetData(outputVector, 0)

      vtkNew<vtkPolyData>
          polydata;
  vtkNew<vtkPoints> points;
  points->InsertNextPoint(0.0, 0.0, 0.0);
  polydata->SetPoints(points.GetPointer());

  // output = polydata.GetPointer(); //doesn't work
  output->ShallowCopy(polydata.GetPointer());

  return 1;
}

//----------------------------------------------------------------------------
void vtkTestReader::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);

  os << indent << "File Name: " << (this->FileName ? this->FileName : "(none)")
     << "\n";
}

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(PolyDataAlgorithmReader)

find_package(VTK COMPONENTS 
  CommonCore
  CommonDataModel
)

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

cd PolyDataAlgorithmReader/build

cmake ..

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

make

./PolyDataAlgorithmReader