# Adding 1d physical groups to gmsh model causes errors when convert it to dolfinx mesh

**URL:** <https://fenicsproject.discourse.group/t/adding-1d-physical-groups-to-gmsh-model-causes-errors-when-convert-it-to-dolfinx-mesh/17618>\
**Category:** mesh\
**Created:** [May 15, 2025, 11:59pm UTC](https://fenicsproject.discourse.group/t/adding-1d-physical-groups-to-gmsh-model-causes-errors-when-convert-it-to-dolfinx-mesh/17618 "2025-05-15T23:59:01Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [May 16, 2025, 8:15am UTC](https://fenicsproject.discourse.group/t/adding-1d-physical-groups-to-gmsh-model-causes-errors-when-convert-it-to-dolfinx-mesh/17618/2 "2025-05-16T08:15:19Z")

</div>

> [@quantumtopology](#):
>
> ` #gmsh.model.addPhysicalGroup(1, [line_x_axis], name="x_axis")`

This is because line\_x\_axis is not part of the surface, as seen by calling:

```python
    boundary = gmsh.model.getBoundary([(2, surface)])
    print(f"{boundary=}, {line_x_axis=}")

```

Thus, if you instead add:

```python
    for boundary_dim, boundary_tag in boundary:
        gmsh.model.addPhysicalGroup(boundary_dim, [boundary_tag], tag=boundary_tag)

```

you will get all your outer boundaries tagged.

---

_[View the full topic](https://fenicsproject.discourse.group/t/adding-1d-physical-groups-to-gmsh-model-causes-errors-when-convert-it-to-dolfinx-mesh/17618)._