CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

I have trouble understanding what is your problem. Could you produce a 
minimal example showing the problem with an assertion for example?

Thanks,

Sebastien.


On 04/07/2014 12:45 PM, Marcel wrote:
> Hello,
>
> I've done further evaluations and noticed strange behaviour. The two points 'a' and 
> 'b' I mentioned in the first post do print like this: (defined as 
> CGAL::Point_3<CGAL::Exact_predicates_exact_constructions_kernel>)
>
> a: 0.5 0.5 0.5 (cout << "a: " << a)
> a: 0/1 0/1 0/1 (cout << "a: " << a.x().exact() << a.y().exact() << 
> a.z().exact())
> b: 0.5 0.5 0.5 (cout << "b: " << b)
> b: 0/1 0/1 0/1 (cout << "b: " << b.x().exact() << b.y().exact() << 
> b.z().exact())
>
> The output values are clearly not the same (despite being represented 
> differently).
>
> The values being the same for both points looks fine as the points come from 
> another visual mesh that actually has vertices in the same place (which is 
> the reason why I am doing this).
> Still, these points insist in not being equal (a == b results in "false") and 
> I cannot seem to create a vector from a to b to measure their distance. (Resulting in 
> the assertion error described in the first post) At least one of these circumstances is 
> however necessary to decide if I can ignore that vertex.
>
> So what might cause the different values where just representation is 
> different?
> And why won't CGAL create a vector from a to b for me?
>
> CGAL 3.9 (Ubuntu 12.04 - unfortunately, I couldn't find a backport of CGAL 
> 4.4)
>
> Greetings,
> Marcel
>
> Am 01.04.2014 um 15:58 schrieb Marcel 
> <>:
>
> > Hello!
> >
> > I'm trying to implement CSG operations with Nef_polyhedra on top of a given 
> > framework that uses OpenSG for rendering. Now I can get all the triangle data 
> > from OpenSG, but this results in 36 vertices for a cube as every corner has 3 
> > vertices (for 3 different normals). This is not a closed mesh, therefore CSG 
> > operations on the Nef_polyhedron fail.
> > Despite the problems that might arise from a fixed merging threshold with 
> > complex models, I was trying to merge vertices in close proximity by 
> > referencing the preexisting vertex in the indices array if there is one. 
> > (When iterating over the given triangles)
> >
> > So, first: Is there by chance a more or less convenient method for automatically 
> > merging "close" vertices?
> >
> > Second, the actual problem:
> > When I try to compute the distance between two vertices, an assertion fails:
> >
> > CGAL/Interval_nt.h:89 "!(i>s) Variable used before being intialized (or CGAL 
> > bug)"
> >
> > in the last line of this snippet:
> >
> > CGAL::Point a = positions->at(i); // Setting these equal manually really 
> > makes them equal
> > CGAL::Point b = newPoint;
> > CGAL::Vector vecdiff(b, a);
> >
> > I don't exactly understand what is wrong here. The points are certainly close as they 
> > 'cout' as the same values. Still, they are not equal by means of "a == b". 
> > (And I cross-checked by setting them to the same values.)
> >
> > So, is there either a way to completely avoid doing this manually or can you 
> > tell me what I am doing wrong?
> >
> > Greetings,
> > Marcel
> >
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