CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Read this:
http://www.cgal.org/FAQ.html#inexact_NT

and then use Exact_predicates_exact_constructions_kernel

Sebastien.


On 03/06/2012 02:05 PM, Miguel Oliveira wrote:
> Hello
>
> I am sorry I think my previous post is a bit messy :)
>
> I was editing and somehow I cut off the carriage returns.
>
> Anyway, I corrected the message on the online forum so if anyone can
> help please go to
>
> <http://cgal-discuss.949826.n4.nabble.com/Triangle-2-intersection-throws-exception-tp4449736p4449736.html>
> Triangle_2 intersection throws exception
> <http://cgal-discuss.949826.n4.nabble.com/Triangle-2-intersection-throws-exception-tp4449736p4449736.html>
>
> There you can easily read it
>
> Thanks
>
> Miguel
>
> On 03/06/2012 12:47 PM, mriem wrote:
> > Hi I am doing triangle intersection for the creation of a mesh. I use
> > the cgal intersection at
> > http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Kernel_23_ref/Function_intersection.html
> > my objects are of cgal::triangle_2type and the kernel is typedef
> > CGAL::Exact_predicates_inexact_constructions_kernel K; The code is
> > like this: //tx_py are the triangle points where x is the triangle
> > number and y the triangle vertice number CGAL::Triangle_2* t0;
> > //triangle t0 CGAL::Triangle_2* t1; //triangle t1 //make sure the
> > triangles are built in ccw orientation if ((CGAL::Triangle_2(t0_p0,
> > t0_p1, t0_p2)).orientation()>0) t0 = new CGAL::Triangle_2(t0_p0,
> > t0_p1, t0_p2); else t0 = new CGAL::Triangle_2(t0_p0, t0_p2, t0_p1);
> > //make sure the triangles are built in ccw orientation if
> > ((CGAL::Triangle_2(t1_p0, t1_p1, t1_p2)).orientation()>0) t1 = new
> > CGAL::Triangle_2(t1_p0, t1_p1, t1_p2); else t1 = new
> > CGAL::Triangle_2(t1_p0, t1_p2, t1_p1); CGAL::Object result =
> > CGAL::intersection(*t0, *t1); //sometimes this line throws an
> > exception I do literally thounsands of intersections without any
> > problem. However, in some particular cases the intersection throws an
> > exception. I cannot understand why it does. I make sue both triangles
> > are ccw oriented, just in case, and I know they are not degenerate.
> > Heres the case where an exception occurs: //coordinates of the
> > triangle t0 x1 = [3.902000 2.924000 2.917000] y1= [0.769000 0.099000
> > -0.002000] //coordinates of the triangle t1 x2 = [2.917000 4.006000
> > 3.902000] y2= [-0.002000 0.765000 0.769000] Here they are drawed with
> > the vertices indicated triangle_intr_problem The exception is
> > terminate called after throwing an instance of
> > 'CGAL::Assertion_exception' what(): CGAL ERROR: assertion violation!
> > Expr: add <= 2 File:
> > /usr/include/CGAL/Intersections_2/Triangle_2_Triangle_2_intersection_impl.h
> > Line: 129 Any idea why this happens? Thank you very much Miguel
> > ------------------------------------------------------------------------
> > View this message in context: Triangle_2 intersection throws exception
> > <http://cgal-discuss.949826.n4.nabble.com/Triangle-2-intersection-throws-exception-tp4449736p4449736.html>
> > Sent from the cgal-discuss mailing list archive
> > <http://cgal-discuss.949826.n4.nabble.com/> at Nabble.com.