[vtkusers] problem when using vtkExtractUnstructuredGrid

Song Li lisong at vrac.iastate.edu
Wed Apr 2 01:11:16 EST 2003


I have a program use "vtkExtractUnstructuredGrid" to extract pieces from
a big UnstructuredGrid dataset, it works fine with the old vtk files
which don't have FieldData. While if the big dataset has FieldData, it
appears that there is no scalar information in the small piece which was
produced by my program , "(the object of small
data)->GetPointData()->GetScalars()" will return 0.

I compared ASCII files of both big and small vtk files, it seems OK, the
only questionable thing is the line with string "scalar" in:

# vtk DataFile Version 3.0
vtk output
FIELD FieldData 1
scalars 1 273774 float

are the same, no matter in big or small file there is 273774,  while the
numbers follow the other terms reflect the change of size, for example,
in big file is "POINT_DATA 273774", in small file the correspondant line
is "POINT_DATA 21153".

My visualiztion program can handle the big dataset with FieldData or
non-FieldData datasets no matter it is produced by
"vtkExtractUnstructuredGrid" or not.

Any suggestions, comments, solutions??? Thanks!

Song Li
VRAC(Virtual Reality Application Center),Iowa State University
Email: lisong at vrac.iastate.edu
Homepage: http://www.vrac.iastate.edu/~lisong

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