CGAL users discussion list

[Pierre Alliez <>]

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


  

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