# About tetgen using

**URL:** <https://community.freefem.org/t/about-tetgen-using/1180>\
**Category:** General Discussion\
**Created:** [August 27, 2021, 11:04pm UTC](https://community.freefem.org/t/about-tetgen-using/1180 "2021-08-27T23:04:57Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Pablo](https://avatars.discourse-cdn.com/v4/letter/p/ad7895/32.png) [@Pablo](https://community.freefem.org/u/Pablo)\
**Post date:** [August 27, 2021, 11:04pm UTC](https://community.freefem.org/t/about-tetgen-using/1180/1 "2021-08-27T23:04:57Z")

</div>

My question is about the example “cube with balloon” ( from manual ).  
How can I use Tetgen to do a cube without a balloon?.  
This is the problem, the streamlines don’t see an internal surface (for example balloon) as an obstacle. Despite fixing the labels and regions for boundary conditions.  
My geometry (not a balloon) is very complex for use buildlayers.

---

<div class="post-metadata">

**Author:** ![frederichecht](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/frederichecht/32/15_2.png) [@frederichecht](https://community.freefem.org/u/frederichecht)\
**Post date:** [August 28, 2021, 2:59pm UTC](https://community.freefem.org/t/about-tetgen-using/1180/2 "2021-08-28T14:59:33Z")

</div>

Dear user  
See the example  
[FreeFem-sources/tetgenholeregion.edp at master · FreeFem/FreeFem-sources · GitHub](https://github.com/FreeFem/FreeFem-sources/blob/master/examples/3d/tetgenholeregion.edp)