[Gmsh] Zero volume elements in Delaunay 2d triangulation

[=?windows-1252?Q?Jean-Fran=8D=E7ois_Remacle?=]

Jose Paulo Moitinho de Almeida a écrit :
> Hello
>
> I know that the Delaunay triangulation is "experimental", but I was solving 
> the problem of face orientation when post-processing the mesh.
>
> Now, when refining the mesh around a singularity I came to an example where I 
> get 
>
> $ gmsh ref.geo -algo del2d -2 -bgm ref.bgm
> ....
> Warning : Colinear points in circum circle computation
> ....
>
> and the resulting mesh has triangles with colinear nodes.
>
>   

gmsh ref.geo -algo del2d -2 -bgm ref.bgm -rand 1.e-11 

gives a better result. Indeed your mesh has sizes that varies a lot, so it
is better to perturbate less the points of the initial mesh. BTW, if you use
nightly snapshots, try the "very very experimental" 


gmsh ref.geo -algo frontal -2 -bgm ref.bgm -rand 1.e-11 

that produce more regular meshes.

JFR
> I tried two recent versions (gmsh-2.1.2-cvs-20080312 and 
> gmsh-2.1.2-cvs-20080331) which produced slightly different meshes, but the 
> same problem by creating (at least) an element (4782 and 4780) with colinear 
> (on a vertical line) nodes (173, 174 and 175).
>
> Is it just a problem of parameters? Changing the geometry tolerance had no 
> effect.
>
> If it isn't my mistake perhaps this example, with very small elements, can be 
> of use in your tests.
>
> Regards
>
> JP Moitinho
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