[vtkusers] Threshold

[Benedikt Birkenbach]

Dear readers,

I want to use the threshhold-algorithm to get rid of some points in my
dataset, which are not needed. These Points have the z-posistions -99
and the datavalue -99. So I use the function shown below.

vtkUnstructuredGrid * cut(vtkStructuredGrid * grid)
{
	vtkThreshold * nn_source = vtkThreshold::New();
	nn_source->ThresholdByUpper(-98);
	nn_source->SetInput(grid);
	return nn_source->GetOutput();
}

Ok, the structuredGrid is now an unstructured, but all points seem to be
away. The result of the Code

// sg is my vtkStructuredGrid, ug is an unstructured one, cut as above

cout << sg->GetNumberOfPoints() << endl;
ug = cut(sg);
cout << ug->GetNumberOfPoints() << endl;

is

806
0

although there are definitly points left, because if I visualize the
result (ug) everything is fine (all the not wanted points are away).
But if I try to use the ICP-algorithm, I get the error

ERROR: VTK/Hybrid/vtkIterativeClosestPointTransform.cxx, line 274
vtkIterativeClosestPointTransform (0x93995a0): Can't execute with NULL
or empty input

If I use ICP without threshold everything works (but the dataset is
wrong, because those -99 should not be used).
The use of "blanking" to skip the points results in

Generic Warning: In /tmp/Downloads/VTK/Common/vtkMath.cxx, line 604
vtkMath::Jacobi: Error extracting eigenfunctions

when using ICP and I am not sure, what effect this will have.
Any tips or hints are welcome,

regards

Benedikt



-- 
  ____  ____  ____  _  ________________________________________
/ __ \/ __ \|__  || |/ /  Benedikt Birkenbach                 |
|  __/|  __/  / / |   /   RRZK/ZAIK der Universitaet zu Koeln |
| | \ | | \  / /_ |   \                                       |
|_|\_\|_|\_\|____||_|\_\  http://www.uni-koeln.de/RRZK/       |
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