[vtk-developers] Measuring the area of arbitrary polygons

[Philippe Pébay]

So, that should work for non-convex ones too? If so I am going to try this.

Thanks
P

On Tue, Mar 12, 2013 at 5:28 PM, Will Schroeder
<will.schroeder at kitware.com>wrote:

> The last I checked the vtkPolyon triangulate methods work pretty well
> (I've triangulated very complex polygons including the outlines of US
> states, etc.) In the past I've used this in combination with the triangle
> area computing routines.
>
>
>
> On Tue, Mar 12, 2013 at 12:07 PM, Moreland, Kenneth <kmorel at sandia.gov>wrote:
>
>>   I might be mistaken, but I thought the triangulation filter correctly
>> handled concave polygons.  The advice I usually see on the ParaView mailing
>> list when someone's concave polygons are not rendering correctly is to
>> triangulate them.
>>
>>  -Ken
>>
>>   From: Philippe Pébay <philippe.pebay at kitware.com>
>> Date: Tuesday, March 12, 2013 9:53 AM
>> To: David Thompson <david.thompson at kitware.com>
>> Cc: VTK Developers <vtk-developers at vtk.org>
>> Subject: [EXTERNAL] Re: [vtk-developers] Measuring the area of arbitrary
>> polygons
>>
>>   Hello D
>>
>> Thanks for the prompt answer. So this is what I was concerned about :)
>> Namely that there is no way to generically deal with concave polygons at
>> this point. In fact, just finding a correct triangulation is not trivial.
>> One could for instance compute a CDT and remove outside triangles. This
>> would be computationally expensive for large meshes composed of such
>> elements, but is there another choice?
>>
>> Thanks
>> P
>>
>> On Tue, Mar 12, 2013 at 3:31 PM, David Thompson <
>> david.thompson at kitware.com> wrote:
>>
>>> Hi P,
>>>
>>> > Is anyone aware of a routine already available to measure the surface
>>> area of arbitrary planar polygons in VTK, including non-convex ones?
>>>
>>>  I don't know of anything in VTK to handle concave polygons. For convex
>>> ones, I believe the triangulate filter followed by the mesh quality filter
>>> should get you the area of a decomposition of the polygon. Assuming that
>>> the triangulate filter creates pedigree IDs, you could sum areas with
>>> matching pedigree IDs.
>>>
>>>         David
>>
>>
>>
>>
>> --
>> Philippe Pébay, PhD
>> Director of Visualization and High Performance Computing /
>> Directeur de la Visualisation et du Calcul Haute Performance
>> Kitware SAS
>> 26 rue Louis Guérin, 69100 Villeurbanne, France
>> +33 (0) 6.83.61.55.70 / 4.37.45.04.15
>> http://www.kitware.fr <http://www.kitware.fr/>
>>
>>
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>
>
> --
> William J. Schroeder, PhD
> Kitware, Inc.
> 28 Corporate Drive
> Clifton Park, NY 12065
> will.schroeder at kitware.com
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> (518) 881-4902
>



-- 
Philippe Pébay, PhD
Director of Visualization and High Performance Computing /
Directeur de la Visualisation et du Calcul Haute Performance
Kitware SAS
26 rue Louis Guérin, 69100 Villeurbanne, France
+33 (0) 6.83.61.55.70 / 4.37.45.04.15
http://www.kitware.fr <http://www.kitware.fr/>
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