[vtkusers] Probs with cell search

Hentschel, Bernd hentschel at rz.rwth-aachen.de
Wed Jun 7 11:15:51 EDT 2006

Hi all,

I've got a problem with the cell search algorithm in VTK (i.e.,
vtkPointSet::FindCell(...)). In the past I have encountered several data
sets in which the FindCell routine returned no cell although the point
in question was definitely in the domain. However, these cases tended to
be very rare. 
Now I got a dataset in which a cell search for points, which are known
to lie inside the domain, fails in more than 50% of the cases (i.e. I
try to find the cell for every cell midpoint and the operation fails in
>50%). This behaviour seems to be dataset specific. The question now is:
Is the data set simply "badly behaved" or should it work anyway? 
I already had a quick glance at the marching scheme implemented inside
FindCell and it seems that the marching process very often reaches its
maximum distance of 12 cells before the correct cell is found.
Since I need this to work quite urgently, the next question would be if
there is some kind of obvious workaround? If need be I can provide
example code and test data to whomever is interested in this.


Dipl.-Inform. Bernd Hentschel
Virtual Reality Group
Center for Computing and Communication (CCC)
RWTH Aachen University 

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