[vtk-developers] Measuring the area of arbitrary polygons

[Will Schroeder]

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
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> 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
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