CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

On mercredi 08 juin 2011 15:31:24 Fabio Casado Ruiz wrote:
> On 6/8/2011 1:20 AM, Andreas Fabri wrote:
> > On 06/06/2011 04:17, Fabio Casado Ruiz wrote:
> >> Hi everyone, I'm trying to make some comparisons between meshes
> >> generated using both TetGen as CGAL. Tetgen statistics for generated
> >> meshes are pretty detailed, but for CGAL (and I must admit that
> >> because of time issued I'm only using the Mesh_3 demo) there are a
> >> few statistics I dont comprehend fully. Is there a place where the
> >> demo, its way of functioning and statistics are explained? I'm
> >> interested in facet angles (this are the angles of superficial faces
> >> right?), the dihedral angle (these are showned in the diagram at the
> >> bottom of the window right?) and the tet. max size (does this size
> >> refer to tetrahedral volumes?).
> >> 
> >> Another issue is the aspect (visually) of final meshes. I've
> >> generated a couple, and when I look at them I can see places where
> >> the original borders are not included (see example pictures). Is this
> >> because CGAL doesnt conform to boundaries????
> > 
> > Hi Fabio,
> > 
> > Did you run the demo that comes with CGAL to produce this mesh?
> > There the sharp edges should appear nicely, as the demo first
> > detects sharp features and then passes the polyline describing
> > them to the mesh generation function.
> > 
> > http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Mesh_3/Chapter_mai
> > n.html#Subsection_49.3.5
> > 
> > 
> > andreas
> > 
> >> Please I would appretiate your help a lot . Thanks again, Fabio.
> 
> yes, im using the CGAL demo. de model is actually really simple, im
> attaching it. i mesh with the same parameters the demo suggests. im
> using cgal3.8 (beta1). i include again the image file showing how the
> final mesh doesnt conform to the boundary lines. can u help? i wanted to
> show two meshes, one done in tetgen and one done in cgal, and i always
> expected cgal's to be better (even do it would be generated in a little
> extra time).

CGAL Mesh_3 demo has not been updated after the new version of Mesh_3 that is 
in CGAL-3.8. Whereas the package, in CGAL-3.8, can mesh a that has sharp 
edges, the code that is used in the demo can only mesh a smooth polyhedron 
(that means it does not respect sharp edges if the polyhedron is not smooth).

Have a look at the examples examples/Mesh_3/. There are several examples that 
show how to mesh a polyhedron that have sharp edges.

-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/