Find the coordinates of a triangle in a mesh

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Florian Spicher
Florian Spicher 2021-11-3
评论： Camille Grimaldi 2023-2-6
I am working with a 2D mesh generated by Gmsh and here I'd like to compute the area of the triangles of in my mesh. What I don't understand is how can I find the coordinates of a given triangle?
In my .m file, I have: msh.nbNod, msh.POS, msh.Max and msh.MIN, msh.LINES, msh.TRIANGLES and msh.PNT.
I think I should somehow use msh.TRIANGLES but I don't get what the numbers listed refer to. If needed, I can post my .m file. Thanks for the help.

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Dave B
Dave B 2021-11-3
编辑：Dave B 2021-11-3
Ran in:
It looks to me like msh.TRIANGLES is referring to indices in msh.POS, which like a reasonable way to describe a mesh.
I'd grab the co-ordinates of a triangle's vertices like this:
squareRing;
triangle_ind=500;
msh.POS(msh.TRIANGLES(triangle_ind,1:3)',:)
ans = 3×3
-1.1902 -0.8650 0 -1.1905 -1.0510 0 -1.3512 -0.9948 0
(Here each row is a vertex, and the columns are x,y,z)
I say it's reasonable, because this is similar to what patch would use (and because max(msh.TRIANGLES(:))==size(msh.POS,1)).
patch('Faces',msh.TRIANGLES(:,1:3),'Vertices',msh.POS,'FaceColor','none','EdgeColor','r')
Note that in the data file you provided, the third column of msh.POS is all zeros, which I assume means that they are all in a 2-D plane.
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Florian Spicher
Florian Spicher 2021-11-4
Aha! Now it’s 100% clear! Well, thank you very much :) you really helped
Camille Grimaldi
Camille Grimaldi 2023-2-6
Hi
How did you get the xy for each triangle in the first place?
Cheers
Camille

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