# [Gmsh] Atypical, newbie question

Vincent Huber vincent.huber at cemosis.fr
Thu Mar 31 21:33:04 CEST 2016

```Hi Julius,

I guess you have to define theses points as Physical Points, isn’t it ?

All the best,

VH
​

2016-03-31 17:54 GMT+02:00 Julius Bier Kirkegaard <juliusbierk at gmail.com>:

> Dear all,
>
> I have (I think) a fairly simple question, but it's also quite atypical,
> so I have had no luck Googling. I hope that you one of you might have time
> to point me in the right direction...
>
> I have a box:
>
> box_size = 50;
> lb = 10.;
> Point(1) = {-box_size/2, -box_size/2, -box_size/2, lb};
> Point(2) = {box_size/2, -box_size/2, -box_size/2, lb};
> Point(3) = {box_size/2, box_size/2, -box_size/2, lb};
> Point(4) = {-box_size/2, box_size/2, -box_size/2, lb};
> Line(1) = {1, 2};
> Line(2) = {2, 3};
> Line(3) = {3, 4};
> Line(4) = {4, 1};
> Line Loop(5) = {1, 2, 3, 4};
> Plane Surface(6) = {5};
> Extrude {0, 0, box_size} {
>   Surface{6};
> }
>
> This works quite well and gmsh is happy to (3D) mesh it.
>
> The problem is that I would to ensure that certain points inside the box
> are node points. So my question is, how do I ensure that points, like these
>
> lc = 10;
> Point(5) = {7.150548, 1.000000,  -6.990684, lc};
> Point(6) = {-4.438894, 1.000000,  -8.960816, lc};
> Point(7) = {-9.893936, 1.000000,  1.452595, lc};
> Point(8) = {-1.675894, 1.000000,  9.858569, lc};
> Point(9) = {8.858176, 1.000000,  4.640336, lc};
> Point(10) = {1.675894, 4.750000,  -9.858569, lc};
> Point(11) = {-8.858176, 4.750000,  -4.640336, lc};
> Point(12) = {-7.150548, 4.750000,  6.990684, lc};
> Point(13) = {4.438894, 4.750000,  8.960816, lc};
> Point(14) = {9.893936, 4.750000,  -1.452595, lc};
> Point(15) = {7.150548, 8.500000,  -6.990684, lc};
>
> are part of the mesh nodes?
>
> The reason I need this is that I need to impose boundary conditions at
> these specific points.
>
> Thank you all in advance.
>
> Best wishes,
> Julius
>
>
>
>
>
>
>
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>

--
Docteur Ingénieur de recherche
CeMoSiS <http://www.cemosis.fr> - vincent.huber at cemosis.fr
Tel: +33 (0)3 68 8*5 02 06*
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