# Limiting Bounds of Planes when Defining Geometry

**URL:** <https://openmc.discourse.group/t/limiting-bounds-of-planes-when-defining-geometry/2521>\
**Category:** User Support\
**Created:** [December 1, 2022, 10:16pm UTC](https://openmc.discourse.group/t/limiting-bounds-of-planes-when-defining-geometry/2521 "2022-12-01T22:16:32Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![willia.smith-14](https://avatars.discourse-cdn.com/v4/letter/w/ecb155/32.png) [@willia.smith-14](https://openmc.discourse.group/u/willia.smith-14)\
**Post date:** [December 1, 2022, 10:16pm UTC](https://openmc.discourse.group/t/limiting-bounds-of-planes-when-defining-geometry/2521/1 "2022-12-01T22:16:32Z")

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I am currently trying to write a conversion tool from a USD file format that will take vertices of a mesh (ie 3 or 4 points that each would represent a mesh surface element) and convert it to a geometry useable in OpenMC.

a) Is there an easy way to do this that I am missing?  
OR  
b) Is there any way to define surfaces or planes such that they bound a 3D region with 2D triangular and tetrahedral elements

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**Author:** ![Shimwell](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/shimwell/32/3876_2.png) [@Shimwell](https://openmc.discourse.group/u/Shimwell)\
**Post date:** [December 2, 2022, 11:51am UTC](https://openmc.discourse.group/t/limiting-bounds-of-planes-when-defining-geometry/2521/2 "2022-12-02T11:51:19Z")

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One option would be to use the DAGMC surface mesh geometry which is a collection of triangles.

There is a micro package that takes vertices and outputs a DAGMC geometry that can be run in OpenMC.

> **[GitHub - fusion-energy/vertices\_to\_h5m: Converts mesh vertices and...](https://github.com/fusion-energy/vertices_to_h5m)**
>
> Converts mesh vertices and connectivity to h5m geometry files compatible with DAGMC simulations - GitHub - fusion-energy/vertices\_to\_h5m: Converts mesh vertices and connectivity to h5m geometry fil...

There is also a [discussion](https://openmc.discourse.group/t/how-to-create-unstructured-meshes-for-tallying/2501) on tetrahedral meshes that might be of interest over here

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**Author:** ![willia.smith-14](https://avatars.discourse-cdn.com/v4/letter/w/ecb155/32.png) [@willia.smith-14](https://openmc.discourse.group/u/willia.smith-14)\
**Post date:** [December 3, 2022, 1:37am UTC](https://openmc.discourse.group/t/limiting-bounds-of-planes-when-defining-geometry/2521/3 "2022-12-03T01:37:03Z")

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Thanks! I have started to have a look through this and seems like it should work for my application.