CGAL users discussion list

[Ivan Rychetsky <>]

On Fri, 2011-07-29 at 13:58 +0200, Laurent Rineau (GeometryFactory)
wrote:
> On lundi 25 juillet 2011 12:46:16 
> 
>  wrote:
> > Hello everybody, I am really new to CGAL and now I try to learn 3D mesh
> > generation of the segmented 3D images.
> > In the manual (Chapter 49: 3D Mesh Generation) I have found the following
> > sentence :
> > " The current implementation provides classes to represent domains bounded
> > by isosurfaces of implicit functions, polyhedral domains and domains
> > defined through 3D labeled images. Currently, 1-dimensional features may
> > be defined as segments and polyline segments. "
> > 
> > Please, does it mean that a 1D-feature (line) can be preserved also using
> > meshing of segmented 3D image?
> > I've tried it without success.
> > 
> > I run succesfully two examples shown in the manual: "mesh_3D_image.cpp" 
> > and
> > "mesh_two_implicit_spheres_with_balls.cpp", in the latter it is
> > demonstrated how an edge (polyline) can be preserved. Then I've tried to
> > modify  the file "mesh_3D_image.cpp" to implement 1D sharp feature when
> > using the segmented image. .
> > For that I use input image: "domain.inr", which describes a simple cube of
> > sizes 128x128x128 (one material only).
> [...]
> > Please, can you see what I am missing, or some hints or suggestions?
> > Thank you, Ivan.
> 
> 
> The documentation probably does not say that explicitly but you must 
> specify 
> the parameter 'edge_size' of the Mesh_criteria criteria object, if you use 
> a 
> domain with 1D-features. For example, with your example, I have used:
> 
>   // Mesh criteria
>   Mesh_criteria criteria(edge_size= 3, facet_angle=30, facet_size=6,
>                          facet_distance=4, cell_radius_edge=3, cell_size=4);
> 
> 
> 
> What is more, in the case the 1D-features are a single segment, there was a 
> bug in CGAL-3.8. Apply the attached patch "Triangulation_3-r64962.patch" to 
> your CGAL installation, or override the file 
> "include/CGAL/Triangulation_data_structure_3.h" with the one I attach.
> 
> Using those two modifications, I managed to mesh the cube, with one sharp 
> edge 
> preserved.
> 
> -- 
> Laurent Rineau, PhD
> R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
> Release Manager of the CGAL Project       http://www.cgal.org/
> 

Thank you very much for your response! 
Your reply really helped, now it works for me.
By the way, the documentation DOES explicitly mention the parameter
'edge_size' for 1D features, but I was not able to discover it before
your reply.
Thanks, Ivan Rychetsky.