[vtkusers] Extract Polydata points with same scalar value

[Sara Rolfe]

Hello,

I am attempting to extract points with the same data value from the  
output of a K-Means segmentation.  First I copied the labels into the  
polydata's scalar array.  Then I used vtkClipPolyData to select points  
with one label at a time.  (My goal is to input these to  
vtkPolyDataConnectivity to seperate spatially disconnected clusters).   
I set up the clipping filters as follows:

for (int i = 0; i < inRange[1]+1; i++)
{

	vtkSmartPointer<vtkClipPolyData> clippersTestLo =  
vtkSmartPointer<vtkClipPolyData>::New();
	clippersTestLo->SetValue(i);
	clippersTestLo->SetInput(contourPolydata);
	clippersTestLo->InsideOutOn();
	clippersTestLo->Update();
		
	vtkSmartPointer<vtkClipPolyData> clippersTestHi =  
vtkSmartPointer<vtkClipPolyData>::New();
	clippersTestHi->SetValue(i-1);
	clippersTestHi->SetInputConnection(clippersTestLo->GetOutputPort());
	clippersTestHi->InsideOutOff();
	clippersTestHi->Update();
		
	cout << "Number of points with label " << i << ": " << clippersTestHi- 
 >GetOutput()->GetNumberOfPoints() << endl;
}

This output number of points is incorrect but close to the right  
number, for example, 19770 points with label 0 instead of the actual  
19783.  I'd appreciate any ideas on where this error is coming from.   
Or is there a better solution for extracting these points so I can  
input them into vtkPolyDataConnectivity?

Thanks,
Sara
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