[vtkusers] compute polygon centroids and normals

[Mathieu Malaterre]

Hi Matt and Elizabeth ,

You can have a look to this class that compute the normals:
http://public.kitware.com/VTK/doc/nightly/html/classvtkPolyDataNormals.html

But for the centroids I don't know...you may adapted this class ?

HTH
mathieu


Matt and Elizabeth Kay wrote:

> Hi all-
>
> I am computing the centroid of each polygon in a
> vtkpolydata (which are triangles) as well as the
> normal of each triangle. I have done this by
> extracting the verticies of each triangle and
> computing the centroid by taking the average of the 3
> verticies. I am fitting a plane to the verticies to
> get the normal of each triangle. I feel like I am
> reinventing the wheel - I have looked but I haven't
> found a vtk function that does this. Any suggestions?
>
> Also- how can I order verticies in my polydata such
> that they are always referenced clockwise or
> counterclockwise for each triangle? I am thinking this
> may help with providing consistently oriented normals
> (ie: outward or inward). Any suggestions would be
> greatly appreciated!
>
> Thanks in advance,
> Matt
>
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Malaterre, Mathieu
The John P. Robarts Research Institute
Imaging Research Laboratories
http://www.imaging.robarts.ca/~mmalat