Re: compute node normal on exterior surface of mesh

[Konstantinos Poulios]

Dear Anne-Cecile

It is easy to get averaged normals on a mesh_fem:

m=gf.Mesh("load", "ladder.mesh")
md=gf.Model("real")
m.set_region(99,m.outer_faces())
mf=gf.MeshFem(m,3)
mf.set_classical_fem(1)
U=md.interpolation("Normal",mf,99)
mf.export_to_vtu("normals.vtu", mf, U, "Normals")

you can then interpolate U on some given points with computer_interpolate_on.

However, I would rather recommend a solution with faces rather than points. Averaging unit vectors leads in general to non-unit vectors. Moreover, points in general do not make sense in a physical world. Surfaces and volumes do. I would recommend you to use the outer_faces_with_direction function. For example with

m.set_region(99,m.outer_faces_with_direction([0,1,0],0.9))

you can define a region with outer normals pointing approximately in the positive Y direction.

Best regards

Kostas

On Thu, Feb 3, 2022 at 12:22 AM Lesage,Anne Cecile J <AJLesage@mdanderson.org> wrote:

Dear all

 

I see in the python documentation that  the mesh class has a function normal_of_face

 

I would like to compute the mean normal at node points (mean of the faces normal to which this point belong) on the exterior surface of the mesh

I have the list of those points id

 

This is to do a direction test for setting boundary conditions

 

Thank you

Regards

Anne-Cecile

 

 

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