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- From: Monique Teillaud <>
- To:
- Subject: Re: [cgal-discuss] Circular Arc imprecision in arrangements
- Date: Thu, 12 May 2011 20:49:58 +0200
Le 12/05/11 19:32, Jan-Hinrich Kaemper a écrit :
Monique Teillaud wrote:
The endpoints of your input line segments have non-rationalYes that is exactly the problem.
coordinates, apparently because they are constructed from lines and
conics. So, their coordinates are algebraic numbers of degree 2.
Then you want to construct circular arcs whose endpoints are such
algebraic points.
If you use CGAL::Arr_circular_line_arc_traits_2<CircularKernel>Ok maybe I will use that traits class instead.
then there are several ways in which circular arcs can be constructed,
and some of them take algebraic points and endpoints, and keep their
coordinates exact.
Hopefully you can find one constructor that works for you, see
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Circular_kernel_2_ref/FunctionObjectConcept_CircularKernel--ConstructCircularArc_2.html#Cross_link_anchor_803
So I understand this right that algebraic endpoints can be any points
with float coordinates?
See above, algebraic endpoints are points whose coordinates are algebraic numbers of degree two.
CGAL::Exact_circular_kernel_2 handles such coordinates in an _exact_ way.
If you use floats instead, ie. if you approximate the algebraic numbers, then you will again meet the problems that you mentioned in your initial email: merged faces, gaps, etc, not even speaking of possible code crashes...
No I don't really any thing other than straight lines and circular arcs.
So in fact the traits-class you propose is more suitable for my purposes.
Thanks a lot, Jan
What I do until now is taking rational coordinates very close to the
original endpoints and use those as endpoints for the circular arc.
But this
messes up my arrangement, because the nearby faces all get merged
because of
the gap that I introduce. I have to avoid this somehow.
Is there any way to construct circular arcs having the exact two
endpoints
of the original straight line?
And if not, how could I best fix the problem?
--
Monique Teillaud
INRIA Sophia Antipolis - Méditerranée
http://www.inria.fr/sophia/members/Monique.Teillaud/
- [cgal-discuss] Circular Arc imprecision in arrangements, jahikae, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Eric Berberich, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Jan-Hinrich Kaemper, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Eric Berberich, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Jan-Hinrich Kaemper, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Monique Teillaud, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Jan-Hinrich Kaemper, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Monique Teillaud, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Jan-Hinrich Kaemper, 05/12/2011
- Re: [cgal-discuss] Circular Arc imprecision in arrangements, Eric Berberich, 05/12/2011
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