# AlgorithmSource

VTKExamples/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.

Question

### Code¶

AlgorithmSource.cxx

#include <vtkSmartPointer.h>

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

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

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

return EXIT_SUCCESS;
}


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


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.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)
{
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 3.3 FATAL_ERROR)

project(AlgorithmSource)

find_package(VTK COMPONENTS
vtkCommonCore QUIET)
if (NOT VTK_FOUND)
message("Skipping AlgorithmSource: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(AlgorithmSource MACOSX_BUNDLE AlgorithmSource.cxx ) target_link_libraries(AlgorithmSource PRIVATE${VTK_LIBRARIES})
else ()
# include all components
target_link_libraries(AlgorithmSource PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS AlgorithmSource MODULES${VTK_LIBRARIES}
)
endif ()


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.