CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

On Tuesday 19 May 2009 18:20:27 Daniel Russel wrote:
> >>  Surface_3 surface(ellipsoid_function, // pointer to function
> >>                  Sphere_3(CGAL::ORIGIN, 3.5)); // bounding sphere
> >
> > Your bounding sphere is defined with a *squared* radius of 3.5, and
> > clearly
> > that sphere does not bound the surface. In my opinion, you need at
> > least 10 as
> > *squared* radius of the sphere.
> >
> > http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Kernel_23_ref/Class_S
> >phere_3.html
>
> As someone who gets bitten by this periodically when using the surface
> mesher, I would really appreciate if there is were a test in the code
> which could give a better error message if you mess this up.

I do not see any way to discover that a user gives an incorrect bounding 
sphere. The bounding is part of the user input itself. What would be doable 
is the detection that the bounding sphere is completely inside the interior 
of 
the surface (and in that case the mesher fails to discover any initial point).

But that is all. One can, for example, give the equation of a infinite 
implicit surface, such as x^x+y^x-1 = 0, and the bounding sphere gives the 
limit of the output surface mesh (in that case it is very important that the 
tag CGAL::Manifold_with_boundaries_tag is used instead of CGAL::Manifold_tag).

-- 
Laurent Rineau, PhD
Engineer at GeometryFactory
http://www.geometryfactory.com/