CGAL users discussion list

[Maarten Moesen <>]

Dear Laurent,

Thank you for your answer. I'll study
the manual to understand better how to tag regions and surfaces and try
it out.

Best regards,

Maarten 
--
Maarten Moesen, PHD
Polymer Physicist Computational Modeling

HUNTSMAN (Europe) BVBA
Everslaan 45
B-3078 Everberg

Office Phone: 0032 (0) 2 758 9962

"Laurent Rineau (GeometryFactory)" <>
wrote on 10/05/2011 07:08:31 PM:

> On mercredi 05 octobre 2011 10:21:46 Maarten Moesen wrote:
> > Dear all,
> > 
> > I'm currently trying out the sharp-feature preservation of CGAL's
3D mesh
> > generator on a 32-bit machine with MSVC 2008 (version 3.8, with
Laurent
> > Rineau's Triangulation_data_structure_3.h patch applied). My
test geometry
> > is a box having a big sphere cut out from its center. I add  as
1D sharp
> > features  using line segments the circles where the sphere
cuts the sides
> > of the box, as well as the ribs of the box. Unfortunately, the
mesher does
> > not preserve all the features near the circle... most of the
times a few
> > segments are missing. The sample code is below. An example mesh
is also
> > attached.
> 
> Hi Maarten,
> 
> Thanks for your complete report. I was able to reproduce your experiment
> easily.
> 
> Actually the sharp features are preserved: "missing" segments
are actually in 
> the 3D complex. What is missing is the two incident facets!
> 
> Your domain is defined as an implicit surface (iso-surface of a function).
> Because of that, even if the surface of the domain can be decomposed
into 
> patches (separated by sharp curves), the "surface_patch_index"
is 
> the same for 
> all triangles of the mesh. If your domain was able to tag surface
patches 
> differently, with different surface indices, then the topological
criterion
>   CGAL::parameters::facet_topology=CGAL::FACET_VERTICES_ON_SAME_SURFACE_PATCH
> could "fix" the issues you have around sharp curves that
correspond 
> to a small 
> angle (say, less than 30°).
> 
> Another way of fixing that is by decreasing the ratio 
> edge_size/facet_size, or 
> decreasing the facet_distance.
> 
> -- 
> Laurent Rineau, PhD
> R&D Engineer at GeometryFactory          
http://www.geometryfactory.com/
> Release Manager of the CGAL Project       http://www.cgal.org/
> 
> -- 
> You are currently subscribed to cgal-discuss.
> To unsubscribe or access the archives, go to
> https://lists-sop.inria.fr/wws/info/cgal-discuss
>