AlgorithmSource

vtk-examples/Cxx/Developers/AlgorithmSource

Description¶

This example demonstrates how to create a source that returns a custom class. To test that it is working, the class vtkTest1 simply stores a double named 'Value' that is instantiated to the value of 4.5. Example.cxx instantiates a vtkTestSource which produces a vtkTest1.

You will need the following in your CMakeLists.txt file:

find_package(VTK
 COMPONENTS
    CommonCore
    CommonDataModel
    CommonExecutionModel
    FiltersSources
    InfovisCore
)

Question

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

Code¶

AlgorithmSource.cxx

#include "vtkTest1.h"
#include "vtkTestAlgorithmSource.h"

int main(int, char*[])
{
  vtkTestAlgorithmSource* source = vtkTestAlgorithmSource::New();
  source->Update();

  vtkTest1* test = source->GetOutput();
  std::cout << test->GetValue() << std::endl;

  return EXIT_SUCCESS;
}

vtkTestAlgorithmSource.h

#ifndef __vtkTestAlgorithmSource_h
#define __vtkTestAlgorithmSource_h

#include <vtkAlgorithm.h>

class vtkDataSet;
class vtkTest1;

class vtkTestAlgorithmSource : public vtkAlgorithm
{
public:
  static vtkTestAlgorithmSource* New();
  vtkTypeMacro(vtkTestAlgorithmSource, vtkAlgorithm);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  // Description:
  // Get the output data object for a port on this algorithm.
  vtkTest1* GetOutput();
  vtkTest1* GetOutput(int);
  virtual void SetOutput(vtkDataObject* d);

  // Description:
  // see vtkAlgorithm for details
  virtual int ProcessRequest(vtkInformation*, vtkInformationVector**,
                             vtkInformationVector*) override;

protected:
  vtkTestAlgorithmSource();
  ~vtkTestAlgorithmSource();

  // Description:
  // This is called by the superclass.
  // This is the method you should override.
  virtual int RequestDataObject(vtkInformation* request,
                                vtkInformationVector** inputVector,
                                vtkInformationVector* outputVector);

  // convenience method
  virtual int RequestInformation(vtkInformation* request,
                                 vtkInformationVector** inputVector,
                                 vtkInformationVector* outputVector);

  // Description:
  // This is called by the superclass.
  // This is the method you should override.
  virtual int RequestData(vtkInformation* request,
                          vtkInformationVector** inputVector,
                          vtkInformationVector* outputVector);

  // Description:
  // This is called by the superclass.
  // This is the method you should override.
  virtual int RequestUpdateExtent(vtkInformation*, vtkInformationVector**,
                                  vtkInformationVector*);

  virtual int FillOutputPortInformation(int port,
                                        vtkInformation* info) override;

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

#endif

vtkTest1.h

#ifndef __vtkTest1_h
#define __vtkTest1_h

#include <vtkDataObject.h>

class vtkTest1 : public vtkDataObject
{
public:
  static vtkTest1* New();
  vtkTypeMacro(vtkTest1, vtkDataObject);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  vtkGetMacro(Value, double);

protected:
  vtkTest1();
  ~vtkTest1();

private:
  vtkTest1(const vtkTest1&);       // Not implemented.
  void operator=(const vtkTest1&); // Not implemented.

  double Value;
};

#endif

vtkTest1.cxx

#include "vtkTest1.h"

#include <vtkObjectFactory.h>

vtkStandardNewMacro(vtkTest1);

vtkTest1::vtkTest1()
{
  this->Value = 4.5;
}

vtkTest1::~vtkTest1()
{
}

void vtkTest1::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);
}

vtkTestAlgorithmSource.cxx

#include "vtkTestAlgorithmSource.h"
#include "vtkTest1.h"

#include <vtkCommand.h>
#include <vtkInformation.h>
#include <vtkInformationVector.h>
#include <vtkObjectFactory.h>
#include <vtkStreamingDemandDrivenPipeline.h>

vtkStandardNewMacro(vtkTestAlgorithmSource);

//----------------------------------------------------------------------------
vtkTestAlgorithmSource::vtkTestAlgorithmSource()
{
  this->SetNumberOfInputPorts(0);
  this->SetNumberOfOutputPorts(1);
}

//----------------------------------------------------------------------------
vtkTestAlgorithmSource::~vtkTestAlgorithmSource()
{
}

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

//----------------------------------------------------------------------------
vtkTest1* vtkTestAlgorithmSource::GetOutput()
{
  return this->GetOutput(0);
}

//----------------------------------------------------------------------------
vtkTest1* vtkTestAlgorithmSource::GetOutput(int port)
{
  return dynamic_cast<vtkTest1*>(this->GetOutputDataObject(port));
}

//----------------------------------------------------------------------------
void vtkTestAlgorithmSource::SetOutput(vtkDataObject* d)
{
  this->GetExecutive()->SetOutputData(0, d);
}

//----------------------------------------------------------------------------
int vtkTestAlgorithmSource::ProcessRequest(vtkInformation* request,
                                           vtkInformationVector** inputVector,
                                           vtkInformationVector* outputVector)
{
  // Create an output object of the correct type.
  if (request->Has(vtkDemandDrivenPipeline::REQUEST_DATA_OBJECT()))
  {
    return this->RequestDataObject(request, inputVector, outputVector);
  }
  // generate the data
  if (request->Has(vtkDemandDrivenPipeline::REQUEST_DATA()))
  {
    return this->RequestData(request, inputVector, outputVector);
  }

  if (request->Has(vtkStreamingDemandDrivenPipeline::REQUEST_UPDATE_EXTENT()))
  {
    return this->RequestUpdateExtent(request, inputVector, outputVector);
  }

  // execute information
  if (request->Has(vtkDemandDrivenPipeline::REQUEST_INFORMATION()))
  {
    return this->RequestInformation(request, inputVector, outputVector);
  }

  return this->Superclass::ProcessRequest(request, inputVector, outputVector);
}

//----------------------------------------------------------------------------
int vtkTestAlgorithmSource::FillOutputPortInformation(int vtkNotUsed(port),
                                                      vtkInformation* info)
{
  // now add our info
  info->Set(vtkDataObject::DATA_TYPE_NAME(), "vtkTest1");
  return 1;
}

//----------------------------------------------------------------------------
int vtkTestAlgorithmSource::RequestDataObject(
    vtkInformation* vtkNotUsed(request),
    vtkInformationVector** vtkNotUsed(inputVector),
    vtkInformationVector* outputVector)
{
  for (int i = 0; i < this->GetNumberOfOutputPorts(); ++i)
  {
    vtkInformation* outInfo = outputVector->GetInformationObject(i);
    vtkTest1* output =
        dynamic_cast<vtkTest1*>(outInfo->Get(vtkDataObject::DATA_OBJECT()));
    if (!output)
    {
      output = vtkTest1::New();
      outInfo->Set(vtkDataObject::DATA_OBJECT(), output);
      output->FastDelete();
      this->GetOutputPortInformation(i)->Set(vtkDataObject::DATA_EXTENT_TYPE(),
                                             output->GetExtentType());
    }
  }
  return 1;
}

//----------------------------------------------------------------------------
int vtkTestAlgorithmSource::RequestInformation(
    vtkInformation* vtkNotUsed(request),
    vtkInformationVector** vtkNotUsed(inputVector),
    vtkInformationVector* vtkNotUsed(outputVector))
{
  // do nothing let subclasses handle it
  return 1;
}

//----------------------------------------------------------------------------
int vtkTestAlgorithmSource::RequestUpdateExtent(
    vtkInformation* vtkNotUsed(request), vtkInformationVector** inputVector,
    vtkInformationVector* vtkNotUsed(outputVector))
{
  int numInputPorts = this->GetNumberOfInputPorts();
  for (int i = 0; i < numInputPorts; i++)
  {
    int numInputConnections = this->GetNumberOfInputConnections(i);
    for (int j = 0; j < numInputConnections; j++)
    {
      vtkInformation* inputInfo = inputVector[i]->GetInformationObject(j);
      inputInfo->Set(vtkStreamingDemandDrivenPipeline::EXACT_EXTENT(), 1);
    }
  }
  return 1;
}

//----------------------------------------------------------------------------
// This is the superclasses style of Execute method.  Convert it into
// an imaging style Execute method.
int vtkTestAlgorithmSource::RequestData(
    vtkInformation* vtkNotUsed(request),
    vtkInformationVector** vtkNotUsed(inputVector),
    vtkInformationVector* vtkNotUsed(outputVector))
{
  // do nothing let subclasses handle it
  return 1;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(AlgorithmSource)

find_package(VTK COMPONENTS 
)

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

Download and Build AlgorithmSource¶

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

cd AlgorithmSource/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:

./AlgorithmSource

WINDOWS USERS

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