[vtk-developers] Measuring the area of arbitrary polygons

[Moreland, Kenneth]

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<mailto:philippe.pebay at kitware.com>>
Date: Tuesday, March 12, 2013 9:53 AM
To: David Thompson <david.thompson at kitware.com<mailto:david.thompson at kitware.com>>
Cc: VTK Developers <vtk-developers at vtk.org<mailto: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<mailto: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



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