CGAL users discussion list

[Ben Supnik <>]

The experts will correct me I am sure, but ...

This is an exact predicate, inexact construction kernel.

If I understand correctly, this kernel can tell you IF the triangle is 
degenerate, but if it is not degenerate it might still NOT be able to 
calculate the area properly, since the underlying numeric type (double) 
can round out.

Try using CGAL::Quotient<CGAL::MP_Float> instead of double...if things 
get better maybe it's a construction issue?

cheers
ben

Panagiotis Foteinos wrote:
> I am using the  CGAL::Filtered_kernel<CGAL::Cartesian<double> > kernel.
>
> On Fri, Aug 28, 2009 at 5:27 PM, Ben Supnik < 
> <mailto:>> wrote:
>
>     What Kernel are you using?
>
>
>     Panagiotis Foteinos wrote:
>
>         Hello everybody.
>
>         I observed something strange.
>
>         If a triangle t(p, q, r) is close to a degenerate one with the
>         value, however, of the predicate t.is_degenerate() always being
>         FALSE, then during the calculation of CGAL::squared_radius(p, q,
>         r), the assertion:
>
>         
> ********************************************************************************************
>           terminate called after throwing an instance of
>         'CGAL::Assertion_exception'
>          what():  CGAL ERROR: assertion violation!
>         Expr: ! CGAL_NTS is_zero(den)
>         File:
>         /scratch/local/CGAL-3.4/include/CGAL/constructions/kernel_ftC2.h
>         Line: 60
>         
> ********************************************************************************************
>
>         is trigerred, and the calculation fails.
>
>         Unfortunately, this error is difficult to be reproduced, but
>         sometimes it happens.
>
>
>         Is this behavior expected? Is it relevant to the fact that the
>         triangle is almost degenerate?
>
>
>         Thank you,
>         Panagiotis
>
>
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