[vtk-developers] vtkStripper bug ?

[Will Schroeder]

This is good to hear :-) I think what may be happening, and this is a
guess, is that if the contours are manifold and *closed" then they will
traverse and then join to form a closed loop. However if they are open
(e.g., intersect the boundary) then they may be separated into pieces,
typically two pieces. This is because a starting point is somewhat
arbitrarily selected and the loop traversed until it comes back to the
starting point, or ends at a boundary.

On Thu, Feb 9, 2017 at 10:14 AM, Andras Lasso <lasso at queensu.ca> wrote:

> We use vtkStripper extensively for creating closed contours from surface
> mesh/image slice intersections of medical images and it works very well. It
> rarely fails, even for complex geometry. We just had to set MaximumLength
> to 10000 to avoid splitting of contours.
>
>
>
> Andras
>
>
>
> *From:* vtk-developers [mailto:vtk-developers-bounces at vtk.org] *On Behalf
> Of *Will Schroeder
> *Sent:* February 9, 2017 8:02
> *To:* Mathieu Westphal <mathieu.westphal at kitware.com>
> *Cc:* VTK Developers <vtk-developers at vtk.org>
> *Subject:* Re: [vtk-developers] vtkStripper bug ?
>
>
>
> I do not believe that the filter makes any guarantee that segments are
> connected into a single polyline (i.e., an optimality condition). It's a
> very simple algorithm and to do that, you'd probably have to do a
> multi-pass, graph analysis... there are situations in the general case
> where polylines could meet at multiple points etc and to extract the fewest
> number of polylines containing the maximal number of segments is
> non-trivial. If you assume manifold conditions, you could simplify the
> algorithm, but it would then require a backward and forward tracing of
> connected line segments, followed by a restart of the joining algorithm.
> This is left as an exercise for the user :-)
>
>
>
> On Thu, Feb 9, 2017 at 2:45 AM, Mathieu Westphal <
> mathieu.westphal at kitware.com> wrote:
>
> Hi
>
> I'm trying to have contour as polyline cells
>
> However, somtimes the contour is separated in two parts, even though the
> part are definitelly connected.
>
> It appears only when the contour is not complete though.
>
> Is it normal ? or a bug ?
>
> Attached is a ParaView example that demonstrate the bug.
>
> Mathieu Westphal
>
>
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> --
>
> William J. Schroeder, PhD
> Kitware, Inc. - Building the World's Technical Computing Software
> 28 Corporate Drive
> Clifton Park, NY 12065
> will.schroeder at kitware.com
> http://www.kitware.com
> (518) 881-4902
>



-- 
William J. Schroeder, PhD
Kitware, Inc. - Building the World's Technical Computing Software
28 Corporate Drive
Clifton Park, NY 12065
will.schroeder at kitware.com
http://www.kitware.com
(518) 881-4902
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