# Combine two regions in 3D

**URL:** <https://community.freefem.org/t/combine-two-regions-in-3d/1814>\
**Category:** General Discussion\
**Created:** [June 17, 2022, 9:12am UTC](https://community.freefem.org/t/combine-two-regions-in-3d/1814 "2022-06-17T09:12:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![RYP](https://avatars.discourse-cdn.com/v4/letter/r/b9e5f3/32.png) [@RYP](https://community.freefem.org/u/RYP)\
**Post date:** [June 17, 2022, 9:12am UTC](https://community.freefem.org/t/combine-two-regions-in-3d/1814/1 "2022-06-17T09:12:00Z")

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Hello, everyone,  
I have two 3D meshes called _mesh1_ and _mesh2_, they have a common border _s_. Now I define a new mesh by _mesh = mesh1 + mesh2_，so _s_ is an internal border of _mesh_. I wonder how to merge two internal regions of _mesh1_ and _mesh2_ into a region so that I can use `tetgreconstruction` to refine grids of the whole region.  
Thanks for all reply.

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<div class="post-metadata">

**Author:** ![RYP](https://avatars.discourse-cdn.com/v4/letter/r/b9e5f3/32.png) [@RYP](https://community.freefem.org/u/RYP)\
**Post date:** [June 19, 2022, 3:03am UTC](https://community.freefem.org/t/combine-two-regions-in-3d/1814/2 "2022-06-19T03:03:56Z")

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I find `extract` can delete internal border，it can solve this problem.