[vtk-developers] vtkStripper bug ?

[Mathieu Westphal]

Thanks for this usefull information.

Mathieu Westphal

On Thu, Feb 9, 2017 at 4:40 PM, Will Schroeder <will.schroeder at kitware.com>
wrote:

> 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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