[Gmsh] Something's Wrong With my High Order Curved Surface Elements

[Jean-François Remacle]

Le 6 avr. 2013 à 21:57, John Pease Moore <jpmoore4 at MIT.EDU> a écrit :

> Hi All,
> 
> I'm trying to create a very simple high order curved mesh of a sphere. When I generate the mesh in gmsh and visualize the surface, everything looks fine. However, when I take the mesh, read it into MATLAB and plot it myself, it looks terrible--it is no longer high order. The polynomial order is 5.
> 

Are you sure you plot it correctly in matlab : in gmsh, we subdivide a lot high order elements for visualization….
There is indeed an option in Gmsh for controlling the subdivision : gmsh -numsubedges 10 refines every mesh edge 
10 times (which represent about 100 subtriangles for one high order triangle).

> I have included three images: two of the sphere generated with gmsh, and another visualized within MATLAB.
> 
> I can't figure out what is causing the discrepancy. I have tried using both monomial and orthonormal (koorwinder) nodal basis functions, but that doesn't seem to help. 
> 
> What type of basis functions does gmsh use? Is it producing its visualization using Bezier curves or nurbs? That's the only explanation I can think of.
> 


we use equidistant lagrange basis (see the documentation for node ordering)


JF

> I am using the following command to generate the mesh:
> gmsh -2 -order 5 -hoOptimize sphere_generator.geo
> 
> Does anyone know what might be going on here? Any help would be greatly appreciated!
> 
> Thanks for your time!
> 
> John
> <mysphereplot.png><spherewedges.png><spherewoedges.png>_______________________________________________
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Prof. Jean-Francois Remacle
Universite catholique de Louvain (UCL)
Ecole Polytechnique de Louvain (EPL) - Louvain School of Engineering
Institute of Mechanics, Materials and Civil Engineering (iMMC)
Center for Systems Engineering and Applied Mechanics (CESAME)
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