PolyDataAlgorithmReader

#include <vtkSmartPointer.h>
#include <vtkPolyData.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 <vtkObjectFactory.h>
#include <vtkStreamingDemandDrivenPipeline.h>
#include <vtkInformationVector.h>
#include <vtkInformation.h>
#include <vtkDataObject.h>
#include <vtkNew.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 
  vtkCommonCore
  vtkCommonDataModel
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping PolyDataAlgorithmReader: ${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(PolyDataAlgorithmReader MACOSX_BUNDLE PolyDataAlgorithmReader.cxx )
  target_link_libraries(PolyDataAlgorithmReader PRIVATE ${VTK_LIBRARIES})
else()
  # 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}
    )
endif()

cd PolyDataAlgorithmReader/build

cmake ..

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

make

./PolyDataAlgorithmReader