CGAL users discussion list

[Laurent Saboret <>]

Hi Alex,

Glad to know that CGAL parameterization works.

Feel free to improve Parameterization_mesh_patch_3 to create a seam between both holes. This is not a case we had in mind when writing this package, thus I am not surprised that it doesn't work out of the box.

Best regards,
Laurent Saboret

Le 19/02/2013 18:43, Alex Tsui a écrit : Hi Laurent,

Thanks, I missed that CGAL can in fact parameterize a topological disk with holes. The example definitely works.

However, for our purposes it would be nice to transform such a mesh into a topological disk with no holes. I guess we could actually cut the mesh and join the holes into a single boundary to get an actual disk, but It seems like we are almost able to do it with Parameterization_mesh_patch_3 by just specifying a cycle through the holes. Although it is currently disallowed in the code, would it be feasible to try to update mesh_patch to support doing this?

--Alex

On Mon, Feb 18, 2013 at 8:59 AM, Laurent Saboret <> wrote:

Hi Alex,

If I remember correctly, CGAL is able to parameterize a topological disk with holes. One may consider your mesh as topological disk with 1 hole, thus it may work.
Did you try the basic parameterization examples, with no cutting algorithm, like e.g. Simple_parameterization?

Best regards,
Laurent Saboret


Le 18/02/2013 17:33, Alex Tsui a écrit :

Hi Laurent,

Yes, I looked at that example, but the simple cutting algorithm assumes that the mesh represents a topological sphere and introduces a cut that makes it a topological disk. What I have is a topological disk ie. mesh with two boundaries, and that algorithm doesn't work on it.

But it's okay - I have already picked a cut that will make the topological disk that I need. The problem that I can't construct the Parameterization_mesh_patch_3 because of the properties of the cut described in my first email.

Thanks,

--Alex

On Mon, Feb 18, 2013 at 1:22 AM, Laurent Saboret <> wrote:
Alex,

CGAL comes with a simple cutting algorithm that may be enough for you. It is available in Complete_parameterization_example or polyhedron_ex_parameterization examples.
Did you try it on your mesh?

Best regards,

Laurent Saboret
Transvalor


Le 15/02/2013 18:38, Alex Tsui a écrit :

Hi,

I would like to compute a planar parameterization on a mesh that is a topological cylinder. First I need to make it a topological disc, and the way to do so is to join the two boundaries with a cut:

http://imgur.com/T6D7DBK

I was hoping to do this with Parameterization_mesh_patch_3 so that I would not have to worry about cutting the mesh myself (and eventually it would be nice to be able to do this on meshes with many more boundaries). However, after specifying the seam, the mesh patch code thinks that I have an invalid patch. I think the trouble is that some vertices appear more than once along the seam (ie. going up and down the middle cut) while some vertices appear only once along the seam (ie. going around the boundaries).

I was wondering if anyone had advice about this?

Thanks,

--Alex

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