# 3D cube with 1D-Line in the middle

**URL:** https://community.freefem.org/t/3d-cube-with-1d-line-in-the-middle/4104
**Category:** General Discussion
**Created:** [October 16, 2025, 11:40pm UTC](https://community.freefem.org/t/3d-cube-with-1d-line-in-the-middle/4104 "2025-10-16T23:40:05Z")
**Posts on this page:** 1
**Showing post:** 4

<div class="post-metadata">

### Author: ![fb77](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/fb77/32/3796_2.png) [@fb77](https://community.freefem.org/u/fb77)
#### Post date: [October 17, 2025, 8:10pm UTC](https://community.freefem.org/t/3d-cube-with-1d-line-in-the-middle/4104/4 "2025-10-17T20:10:08Z")

</div>

There is no built-in command to build this meshL from the 3d mesh. What you can do is copy by hand the 1d data from the file .mesh and put them to another file, so that you can read it with FreeFem to build the meshL, by adapting to x,y,z components the example of [Input Border Data from an External File in FreeFEM++ - #3 by fb77](https://community.freefem.org/t/input-border-data-from-an-external-file-in-freefem/3713/3)  
which has only x,y components.  
At the end instead of `mesh Th=buildmesh(a(nborder));`  
you can do meshL `ThL=buildmeshL(a(nborder));`  
Anyway I don’t see what you want to do afterwards, since in FreeFem line integrals cannot be used in variational formulations for 3d finite elements.

---

_[View the full topic](https://community.freefem.org/t/3d-cube-with-1d-line-in-the-middle/4104)._