CGAL users discussion list

[Marc Pouget <>]

Puzzling!

can you try a real planar plane and a simple smooth surface  
(parabolic cylinder or elliptic paraboloid there is a picture in the  
manual 53.2) to see if the results are as expected and hence check  
there is not pb in the interface?

Marc



On 14 , Oct , 2009, at 11:06 , Thorben Kröger wrote:

> On Wednesday 14 October 2009 07:52:02 Marc Pouget wrote:
> > One thing is surprising on this picture:
> >
> > all the vertices on a "line" of the mesh should have the same
> > computed differential quantities, cause the mesh is regular and the
> > patches symmetric, so the estimations are only done on translates. So
> > i think there may be a bug in the way neighbors are retrieved, you
> > may want to check and compare the patches for vertices along the same
> > "line". Note that if this is the problem, it is only related to the
> > example code and not the core of the package.
>
> I have modified my plane example to output the values computed for  
> another
> point translated in x-direction along the plane, it should receive  
> the same
> normal vector.
>
> in plane_01.png, I have added the point to the right (it's located  
> where the
> arrow originate) and it's neighors, again painted in blue '*'. The  
> top view
> plane_03.png shows that the neighborhood is not completely the  
> same, but
> close. I would have thought that using such a large neighborhood  
> would be
> robust to such slight changes?
>
> The side view is plane_02.png, the two red vectors are the ones  
> estimated by
> CGAL for the two neighborhoods.
>
> Any thoughts?
>
> Cheers,
>
> Thorben
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> discuss<plane_03.png><plane_02.png><plane_01.png>