[vtkusers] question ? [fill contour]

[David Gobbi]

On Fri, Apr 4, 2014 at 8:24 AM, Dr. Roman Grothausmann
<grothausmann.roman at mh-hannover.de> wrote:
> Dear David,
>
> Many thanks for Your answer, that explains the behaviour.
> If now the problem that vtkContourTriangulator has trouble closing nested
> loops, which I can understand isn't easy, see attached images.

Detecting such loops was never one of my objectives, unfortunately.
I was only aiming to fill the sort of contours that one would get by
applying a threshold to a scalar field.

> I'm now banging my head around how to help vtkContourTriangulator by e.g.
> breaking the nested loops into single loops. I only can think of a way to
> get one single loop but then not all other possible single loops.
> Delauney2D goes in the right direction but is not completely correct.
> Is this a problem that cannot be solved?

VTK has lots of filters that have "Graph" as part of their name, look
through them to see if one of them does what you need.

  David


> On 01/04/14 15:13, David Gobbi wrote:
>>
>> Hi Roman,
>>
>> That's very interesting, but not really unexpected. Take a look
>> at the function vtkContourTriangulator::TriangulateContours in
>> vtkContourTriangulator.cxx, and you will see that the first two
>> operations are loop detection (vtkCCSMakePolysFromLines)
>> followed by the creation of polygons from "incomplete" loops
>> (vtkCCSJoinLooseEnds).
>>
>> Cheers,
>>
>>    David
>>
>> On Tue, Apr 1, 2014 at 2:38 AM, Dr. Roman Grothausmann
>> <grothausmann.roman at mh-hannover.de> wrote:
>>>
>>> Hi David,
>>>
>>>
>>> Many thanks for that contribution. I just checked if this filter can also
>>> be
>>> used to solve my current problem of identifying/closing loops in graphs.
>>> In
>>> a way it can but not in any case. For example if the graph of a 3d
>>> skeleton
>>> has loops only some are closed by vtkContourTriangulator. Additionally,
>>> vtkContourTriangulator also spans triangles over Y-shaped regions. Some
>>> exemplary images are attached for the tree cases.
>>>
>>> Best wishes
>>> Roman
>
>
> --
> Dr. Roman Grothausmann
>
> Tomographie und Digitale Bildverarbeitung
> Tomography and Digital Image Analysis
>
> Institut für Funktionelle und Angewandte Anatomie, OE 4120
> Medizinische Hochschule Hannover
> Carl-Neuberg-Str. 1
> D-30625 Hannover
>
> Tel. +49 511 532-9574