CGAL users discussion list

[Graham Macpherson <>]

Hello Pierre,

That parameter was at 0.001 in my initial post, if I change it to 0.0008 it 
triples the number of points on the surface (they form in clumps, not 
uniformly distributed), but there is exactly the same magnitude of radius 
error.

If I make it 0.0005, my PC runs out of memory (8GB RAM) before it completes.

If I make it 0.1, I get essentially the same result as 0.001.

Regards,

Graham


On Friday 14 August 2009 14:27:32 Pierre Alliez wrote:
> hi Graham,
>
> have your tried tuning the third parameter if the surface? the relative
> precision of the dichotomy mechanism to find the intersection?
>
> Pierre Alliez
> INRIA Sophia Antipolis - Mediterranee
> Project-team GEOMETRICA
> http://www-sop.inria.fr/members/Pierre.Alliez/
> Tel: +33 4 92 38 76 77
> Fax: +33 4 97 15 53 95
>
> Graham Macpherson a écrit :
> > Hello,
> >
> > I'm meshing surfaces using the implicit surface mesher and testing it
> > with simple smooth shapes.  Using the example
> >
> >     examples/Surface_mesher/mesh_an_implicit_function.cpp
> >
> > I've created a fairly fine surface of a sphere using the criteria:
> >
> >         30.0, // angular bound
> >         0.01, // radius bound
> >         0.001  // distance bound
> >
> > The surface is not smooth - it has an "orange peel" look.  Plotting the
> > radius of each vertex of the triangulation shows the magnitude of error
> > of the triangulation point positions from the expected radius of 1:
> >
> >     fineSphereSurfaceWithRadius.png
> >
> > Creating a coarse surface with criteria
> >
> >         30.0, // angular bound
> >         0.1, // radius bound
> >         0.1  // distance bound
> >
> > Results in:
> >
> >     coarseSphereSurfaceWithRadius.png
> >
> > where the magnitude of vertex error is similar, but in the fine case, the
> > same radial vertex position error in a smaller triangle creates a bigger
> > error in the normal direction, hence the uneven look.
> >
> > Is this the result that is expected? and is there anything that I can do
> > to improve the conformance of the triangulation points to the expected
> > sphere function?  Am I missing a tolerance adjustment somewhere?
> >
> > It isn't a write precision/truncation problem, as I've set the precision
> > of the ofstream to 15.
> >
> > Thanks,
> >
> > Graham
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> >
> >
> > ------------------------------------------------------------------------