[vtkusers] vtk polydata to image data

[AIs]

Hi VTK Users,
I am trying to convert vtk Polydata in to image data.
I have followed this example
http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/PolyDataToImageData 
and it works. But when I use a polydata  generated from a images I am unable
to generate a image data from the polydata. Following is my code,

vtkSmartPointer<vtkDICOMImageReader> dimg =
vtkSmartPointer<vtkDICOMImageReader>::New( );
dimg->SetDirectoryName( "C:/Users/Desktop/DS2" );
dimg->SetDataExtent( 0, 511, 0, 511, 1, 62 );
dimg->SetDataOrigin( 0.0, 0.0, 0.0 );
dimg->SetDataSpacing( 1.0, 1.0, 1.0 );
dimg->SetDataByteOrderToLittleEndian( );
dimg->Update( );

//defining contour filter
vtkSmartPointer<vtkContourFilter> cont =
vtkSmartPointer<vtkContourFilter>::New( );
cont->SetInputConnection( dimg->GetOutputPort( ) );
cont->SetValue( 0, 148 );

vtkSmartPointer<vtkPolyData> pd = cont->GetOutput( );

cont->Update( );

// defining image data
vtkSmartPointer<vtkImageData> idata = vtkSmartPointer<vtkImageData>::New( );

// defining bounda for the image data
double bounds [ 6 ];
pd->GetBounds( bounds );
// define spacing 
double spacing [ 3 ];
spacing [ 0 ] = 0.5;
spacing [1 ] = 0.5;
spacing [ 2 ] = 0.5;

idata->SetSpacing( spacing );

// computing dimensions
int dim [ 3 ];
for ( int i = 0; i < 3; i++ ) {
	dim [ i ] = static_cast<int>( ceil ( ( bounds[ i * 2 + 1 ] -  bounds [ i *
2 ] ) / spacing [ i ] ) );
   }

idata->SetDimensions( dim );
idata->SetExtent( 0, dim [ 0 ] - 1, 0, dim [ 1 ] - 1, 0, dim [ 2 ] - 1 );

double origin [ 3 ];
origin[ 0 ] = bounds [ 0 ] + spacing [ 0 ] / 2 ;
origin [ 1 ] = bounds [ 2 ] + spacing [ 1 ] / 2 ;
origin [ 2 ] = bounds [ 4 ] + spacing [ 2 ] / 2 ;

idata->SetOrigin( origin );

idata->SetScalarTypeToUnsignedChar( );
idata->AllocateScalars( );

// fill image with foreground voxels
unsigned char inval = 255;
unsigned char outval = 0;

vtkIdType cnt = idata->GetNumberOfPoints( );

for ( vtkIdType i = 0; i < cnt; i++ ) {

	idata->GetPointData( )->GetScalars( )->SetTuple1( i, inval );

	}

// polydata to image stencil
vtkSmartPointer<vtkPolyDataToImageStencil> pol2istenc =
vtkSmartPointer<vtkPolyDataToImageStencil>::New( );
pol2istenc->SetInput( pd );
pol2istenc->SetOutputOrigin( origin );
pol2istenc->SetOutputSpacing( spacing );
pol2istenc->SetOutputWholeExtent( idata->GetExtent( ) );
pol2istenc->Update( );

// defining image stencil ( image data )
vtkSmartPointer<vtkImageStencil> istenc =
vtkSmartPointer<vtkImageStencil>::New( );
istenc->SetInput( idata );
istenc->SetStencil( pol2istenc->GetOutput( ) );
istenc->ReverseStencilOff( );
istenc->SetBackgroundValue( outval );
istenc->Update( );
	
// visualization

vtkSmartPointer<vtkPolyDataMapper> spoly =
vtkSmartPointer<vtkPolyDataMapper>::New( );
spoly->SetInputConnection( source->GetOutputPort( ) );
spoly->ScalarVisibilityOff( );

vtkSmartPointer<vtkActor> sact = vtkSmartPointer<vtkActor>::New( );
sact->SetMapper( spoly );

vtkSmartPointer<vtkImageActor> iact = vtkSmartPointer<vtkImageActor>::New(
);
iact->SetInput( istenc->GetOutput( ) );

vtkSmartPointer<vtkRenderer> ren1 = vtkSmartPointer<vtkRenderer>::New( );
ren1->AddActor( iact );
ren1->SetBackground( 0.2, 0.3, 0.4 );
	
vtkSmartPointer<vtkRenderWindow> renWin1 =
vtkSmartPointer<vtkRenderWindow>::New( );
renWin1->AddRenderer( ren1 );

vtkSmartPointer<vtkRenderWindowInteractor> iren1 =
vtkSmartPointer<vtkRenderWindowInteractor>::New( );
iren1->SetRenderWindow( renWin1 );

renWin1->Render( );
iren1->Start( );

On implementing this code all I get is a black slice  as 2D image data.
I have already tried by changing spacing and bounds but is not able to get
an image data from my generated polydata.
But the same example code works for polydata obtained using sphere source as
followed by implementing the example.
Can some one please guide me as to what am I doing wrong.
Thanking you in advance.
Kind regards.
AIs






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