[vtkusers] Sort unordered set of points clockwise (orcounter-clockwise)

[Miguel Sotaquirá]

Actually the approach you suggested (using feature edges + loop) is the one
I'm using now, and is working without problems.

Thanks!
Miguel


2011/8/1 Adriano Gagliardi <agagliardi at ara.co.uk>

> **
> There is a class in ParaView that will do this for you, but unfortunately
> it is not available in VTK yet. However, it has been flagged up in Mantis.
>
> I've done something similar as you want, but I managed to obtain
> connectivity information first by using extracting feature edges. I
> then order the points in clockwise fashion by doing a simple loop around
> each feature edge (or vtkLine), which would then loop around the rest of the
> edges looking for a common point. This worked for me in the end although for
> a very large number of points it will get slow. The other option is to come
> up with a scalar value that gives you the correct ordering of the points and
> then sort the points based on it (something like value = sqrt(x*x +
> y*y)*(value for direction). Otherwise, I'd check out vtkPlotEdges in the
> ParaView distribution and see if you can integrate it into VTK yourself.
>
> Cheers,
> Adriano
>
> ===================================
>
> Adriano Gagliardi MEng PhD
> Business Sector Leader
> Computational Aerodynamics
> Aircraft Research Association Ltd.
> Manton Lane
> Bedford
>
> Tel: 01234 32 4644
> E-mail: agagliardi at ara.co.uk
> Url: www.ara.co.uk
>
>
>  ------------------------------
> *From:* vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] *On
> Behalf Of *Miguel Sotaquirá
> *Sent:* 30 July 2011 04:14
> *To:* vtkusers at vtk.org
> *Subject:* [vtkusers] Sort unordered set of points clockwise
> (orcounter-clockwise)
>
> Hi,
>
> In 3-D space I have an unordered set of, say, 6 points; something like
> this:
>
>                (A)*
>                               (C)*
> (E)*
>                              (F)*
>          (B)*
>
>                       (D)*
>
> The points form a 3-D contour but they are unordered. For unordered I mean
> that they are stored in a vtkIdList = [A - B - C - D - E - F]. I just want
> to reorganize this list starting from an arbitrary location (let's say point
> A) and traversing the points clockwise or counter-clockwise. Something like
> this:
>
> orderedList = [A - E - B - D - F - C]
> or
> orderedList = [A - C - F - D - B - E]
>
> I'm trying to implement an algorithm as simple as possible, since the set
> of points in mention corresponds to a N-ring neighborhood of each vertex on
> a mesh of ~420000 points, and I have to do this for each point on the mesh.
>
> How can I do this in VTK?
>
> Thanks,
> Miguel
>
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