[Gmsh] 3D mesh crash. Coplanar points warning

[Christophe Geuzaine]

Benjamin SAUTHIER wrote:
> Hello,
> 
> I want to mesh a domain bounded by a 2m long cylinder
> inside an approximately 20*20*25m box.
> 
> The surface mesh of the cylinder is generated by
> extrusion of a circle (Transfinite mesh) to obtain
> quadrangles.
> 
> The characteristic length is max 0.5m at the boundary
> of the box and min 0.06m on the cylinder.
> 
> When generating the 3D mesh I got the  warnings of
> coplanar points and "Unable to add points" statements.
> Ultimately gmsh crashes.

Benjamin - Currently gmsh cannot generate 3D tetrahedral meshes if the 
surface mesh contains quadrangles: we would need to introduce pyramids 
to connect the tets with the quads, and that's not implemented.

Christophe

> 
> I looked at changing characteristic length and random
> perturbation factor but it didn't work. Where does
> this come from? Is there a workaround beside using
> Netgen (this mesh is actually a stripped down version
> of a bigger mesh with mixed hexa and tetra elements).
> 
> I joined the geo files.
> 
> Thx for you help.
> 
> Benjamin
> 
> ------------------------------
> 
> Info    : Meshing surface 66
> Info    : Smoothing surface 66
> Info    : Meshing surface 68
> Info    : Smoothing surface 68
> Info    : Mesh 2D complete (0.793879 s)
> Info    : Mesh 3D...
> Info    : Mesh 3D... (initial)
> Info    : Nod=645/12914 Elm=2600
> Info    : Vol=16464 (346 297 2)
> Info    : Nod=1290/12914 Elm=5185
> Info    : Vol=16464 (662 625 3)
> Info    : Nod=1935/12914 Elm=9473
> Info    : Vol=16464 (846 1085 4)
> Info    : Nod=2580/12914 Elm=14224
> Info    : Vol=16464 (1374 1202 4)
> Info    : Nod=3225/12914 Elm=17741
> Info    : Vol=16464 (1940 1281 4)
> Info    : Nod=3870/12914 Elm=21113
> Info    : Vol=16464 (2508 1357 5)
> Info    : Nod=4515/12914 Elm=24365
> Info    : Vol=16464 (3078 1432 5)
> Warning : Coplanar points in circum sphere computation
> Warning : (3.05,3.59187,20.1245) (3.05,3.575,21.866)
> (3.05,3.46624,21.7934) (3.0
> 5,3.575,20.134)
> Warning : Coplanar points in circum sphere computation
> Warning : (3.05,3.69232,21.9239) (3,3.69232,21.9239)
> (3,3.575,21.866) (3.05,3.57
> 5,21.866)
> Warning : Unable to add point 3175 (will try it later)
> Warning : Unable to add point 3135 (will try it later)
> Warning : Unable to add point 3095 (will try it later)
> Warning : Unable to add point 5055 (will try it later)
> Warning : Unable to add point 161 (will try it later)
> Warning : Unable to add point 351 (will try it later)
> Warning : Unable to add point 1015 (will try it later)
> Warning : Unable to add point 1055 (will try it later)
> Warning : Unable to add point 2975 (will try it later)
> Warning : Unable to add point 1095 (will try it later)
> Warning : Unable to add point 1135 (will try it later)
> Warning : Unable to add point 2935 (will try it later)
> Warning : Coplanar points in circum sphere computation
> Warning : (3.05,4.34625,20.0375) (3,4.31237,20.0286)
> (3.05,4.31237,20.0286) (3,4
> .34625,20.0375)
> Warning : Unable to add point 2895 (will try it later)
> Warning : Unable to add point 2855 (will try it later)
> Warning : Unable to add point 2815 (will try it later)
> Warning : Unable to add point 306 (will try it later)
> Warning : Coplanar points in circum sphere computation
> Warning : (3.05,4.84666,20.364) (3.05,4.77895,20.2898)
> (3.05,4.81205,20.3242) (3
> .05,3.575,21.866)
> Warning : Coplanar points in circum sphere computation
> Warning : (3.05,4.84666,20.364) (3,4.81205,20.3242) (3.05,4.812
> 
> 
> 	
> 
> 	
> 		
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-- 
Christophe Geuzaine
Assistant Professor, Case University, Mathematics
http://www.case.edu/artsci/math/geuzaine