[vtkusers] Problems with vtkPolyData and GlobalIds

[David E DeMarle]

I think you mean point indexes. The globalids array is just a set of
labels for individual elements. It won't matter if global ids values
aren't contiguous or start at zero any more than if and array holding
temperatures for instance is similarly scattered.

Cells use point indices (offsets into the points array) to say which
points they consist of. If the indices do not fall within the range of
that array, you will have the type of problems you are describing. It
won't matter if they don't start at zero or have gaps as long as they
are inside the range of 0..(num_points-1).

David E DeMarle
Kitware, Inc.
R&D Engineer
21 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4909


On Thu, Jun 21, 2012 at 3:14 AM, RE <roccoerdmann at gmx.de> wrote:
> Hey,
>
> i'm currently working on an interface between Nastran and VTK. I've written
> a converter which produces vtk files from Nastran db files. The vtk files
> are extracted in the correct format.
> I think the problem is found within the GlobalIds Array (vtkIdTypeArray)
> which is added to the global id array of the polydata object, since the
> global ids do not start from zero but from i.e. 20001. There are jumps
> within the ids respectively (i.e. 20001 - 20500, 50000 - 51000, ....). Is
> that the reason why i always get degenerated cells? When i read the vtk file
> into the memory, number of points, number of cells, number of ... are
> extracted correct. But polydata.buildlinks(0) (polydata.buildlinks() will
> not be compiled since an argument is needed) will results in crashing (if i
> load a file with ids starting from zero, this methode works correctly). A
> vtkCleanPolyData with input set to the polydata will crash respectively if i
> have jumps within the global ids.
>
> Is there a way to read vtk files with jumps within the globalids?
>
> Regards
>
> RE
>
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