CGAL users discussion list

["Downe, Richard W" <>]

Ah. I naively assumed that a Nef polyhedron guaranteed no self intersections. 
Is there a way to achieve this with Nef polyhedrons? Else...is there a 
workable technique for pruning self intersections without forfeiting 
manifoldness?
-rd

"Sebastien Loriot (GeometryFactory)" 
<>
 wrote:


Don't know if it's related but you do have a self intersection in the
.off provided. You can use in the Polyhedron demo the
"Self intersection " operation to see where it is.

Sebastien.

Richard Downe wrote:
> I'm using the AABB_polyhedral_oracle surface meshing demo code to remesh
> a surface -- basically, I combine 2 or more (6 or 7 is the high side of
> what is common) disjoint tubular meshes using NEF_polyhedron.  The .off
> file I get when I write the NEF_polyhedron to a file is clean, with no
> self intersections, and I can view it in tecplot without difficulty.
>
> The problem comes with the remeshing -- I remesh to smooth the surface
> and guarantee that my triangles are as regular as possible, etc., since
> the downstream processing is computational fluid dynamics.  Most
> surfaces work fine.  The attached surface I continually get
>
> File: /usr/include/CGAL/Surface_mesher/Surface_mesher.h
> Line: 248
> Explanation: (0.0200637 0.0244694 0.0292433) is already inserted on
> surface.
>
> in spite of the fact that the .off file appears to be fine.
> If I set  Tag to Non_manifold, it meshes successfully, but the output
> surface contains a patch where some of the facets are reversed.  I feel
> as though this provides some insight into what might be wrong/breaking,
> but I don't know enough to intelligently pursue it further.  Wondered if
> anyone else might have insight.
> Attached is the .off file from the NEF_polyhedron pre-remshing.  I can
> supply the final mesh as well, but it is quite large, and sending both
> will put me over the attachments size limit, thus if anyone would like
> to see it, let me know and I'll send it along separately.
> Thanks.
> --rd
>


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