[vtkusers] Extracting cell connectivity from a vtk file

[Eric Mark (CISD/CIV)]

Thanks Berk,

That does get me almost to what I'm shooting for.  cell is now a 
vtkTetra and I would like the actual connection list is specified by the 
Point Id's so I can write them out as a string with an index in front of 
them.  ie.         1  232  295  10 19    (index conn1 conn2 conn3 conn4)

I was trying to do this just to see if I could get to the connection 
point ids:

for i in xrange(numcells):
     cellobject = ug.GetCell(i)
     print "CellObject Methods: ", dir(cellobject)
     print " %d, %s " % (j + 1, cellobject.CellBoundry())
     j= j + 1

Thanks,

Eric

Berk Geveci wrote:
> You should be able to do:
>
> ug = r.GetOutput()
> ncells = ug.GetNumberOfCells()
> for i in xrange(ncells):
>   cell = ug.GetCell(i)
>
> The key is to call GetCell() on the unstructured grid not the cell
> array returned by GetCells().
>
> -berk
>
>
> On Fri, Sep 25, 2009 at 11:37 AM, Eric Mark (CISD/CIV)
> <emark at arl.army.mil> wrote:
>   
>> Hello all,
>>
>> I'm using python with vtk 5.2.1 and am trying to read the connectivity list
>> from a vtk file and write it back out in a different format.    I'm able to
>> read the point data but I'm not having any success in reading the
>> connectivity data.    I would like to be able to print out a connectivity
>> list in the same manner that I'm using below to print the points.  However
>> it seems that GetCell or GetNextCell methods are not available from Python.
>>  Am I doing something wrong or is there an alternate way of doing this?
>>
>> Thanks,
>>
>> Eric
>>
>> Here's the code:
>>
>> fn = "test.vtk"
>> r = vtkUnstructuredGridReader()
>>
>> r.SetFileName(fn)
>> r.Update()
>> points = r.GetOutput().GetPoints()
>>
>> print "Number of Points: " ,  points.GetNumberOfPoints()
>> i = 0
>> while(i < points.GetNumberOfPoints()) :
>>    print "Next Point : %d, %s " % (i + 1, points.GetPoint(i))
>>    i = i + 1
>>
>> numcells = r.GetOutput().GetNumberOfCells()
>> print "Number Of Cells: ", numcells
>> cells = r.GetOutput().GetCells()
>> print "Cells Var contains: ", cells
>> print "Cells.GetSize : ", cells.GetSize()
>> print "Cells.GetSize : ", cells.GetNumberOfConnectivityEntries()
>> print "What Can I Do With Cells? :", dir(cells)
>> j = 0
>> cells.SetTraversalLocation(j)
>> print "NextCell", cells.GetOutput().GetCell(j)
>> #print "Check Array: ",  r.GetOutput().GetCells()
>> while(j < cells ):
>>    #print " %d, %s " % (j + 1, cells.GetNextCell())
>>    j = j + 1
>>
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