CGAL users discussion list

Indeed. The sweep-line alg. requires an  
exact-predicate-exact-construction kernel.

It requires exact constructions when it constructs new geometric  
object, for example, intersections points. If, for example, the sweep  
line is used to construct an arrangement of segments that do not  
intersect each other in their interior, then exact constructions is  
not required. Exact predicates are always required.

Quoting "Ben Supnik" 
<>:

> Hi Konstantin,
>
> Is it possible that the sweep-line algorithm requires an  
> exact-pred-exact construction kernel?
>
> Boolean ops are built on top of arrangement, and arrangement does  
> require exact constructions...it needs to "remember" and persist  
> intersection points exactly to maintain topological correctness  
> after inserting curves.
>
> I do not know if this is true for sweep-line or whether sweep-line  
> is capable of comparing intersections based on their input curves...
>
> To the CGAL folks...is there a table or single place in the manual  
> where the kernel requirements for each package are specified?
>
> cheers
> ben
>
> Konstantin Sinitsyn wrote:
> > Hello!
> >
> > I am new to CGAL and currently I have some problems with polygon boolean
> > operations in my application.
> >
> > Look at attched source file, some precondition assertion occurs in sweep
> > line algorithm when calling do_intersect function on two simple
> > polygons. I thing this happens when we have intersections with vertical
> > edges of polygons (with horizontal looks like all ok).
> >
> > PS: I'm using lasted version of CGAL (3.4) and boost (1.39), MSVC 9.0 SP1.
> >
> > Thanks.
> > Konstantin!
>
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