# mesh-editor v3.2.3

**Mercurial revision 5786:5c8b45563631 | 2026-08-04**

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## Description

`mesh-editor` is a tool designed to perform operations on an input grid (mesh). It allows you to modify, transform, and save mesh files in the `.nei` format.

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## Usage

```bash
mesh-editor [OPTIONS] -m input
```

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## Options


| Option         | Description                                                                                   |
| -------------- | --------------------------------------------------------------------------------------------- |
| `-h`, `--help` | Display this help and exit.                                                                   |
| `-m <file>`    | **Required.** Input mesh file (`.nei` format).                                                |
| `-o <name>`    | Output filename. Default: `mesh-editor.nei`.                                                  |
| `--proj`       | Activate projection on a spherical grid. Uses a basic method (see [PROJ](#proj) for details). |
| `--flip`       | Flip the north-south axis.                                                                    |
| `--symetric`   | Add the symmetric mesh relative to the equator to the final mesh.                             |


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### Deprecated Options

> ⚠️ **Warning:** These options are deprecated and may not be supported in future versions.


| Option       | Description                                               |
| ------------ | --------------------------------------------------------- |
| `-p <file>`  | Polygon file to limit the working area for safety checks. |
| `-b <file>`  | Boundary file (`.bel` format).                            |
| `-c`         | Check for channel edges.                                  |
| `-d <float>` | Minimum resolution: merge all smaller connections.        |
| `-e <float>` | (No description available in the original documentation.) |
| `-z`         | Pre-set zone to limit the working area.                   |
| `--debug`    | Activate debug verbose mode.                              |


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(proj)=
## PROJ

When the `--proj` option is enabled, the mesh is projected onto spherical coordinates using the following method:

- **Longitude:** `lon = x * 110. / 100.`
- **Latitude:** `lat = y + acos(100. / 110.) * 180. / PI`

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## Examples

### **Basic Mesh Editing**

Load an input mesh file and save it with the default output name:

```bash
mesh-editor -m input.nei
```

### **Save to a Custom Output File**

Load an input mesh and save it to a custom output file:

```bash
mesh-editor -m input.nei -o output.nei
```

### **Project Mesh on Spherical Coordinates**

Project the mesh onto spherical coordinates:

```bash
mesh-editor -m input.nei --proj -o projected_mesh.nei
```

### **Flip North-South Axis**

Flip the north-south axis of the mesh:

```bash
mesh-editor -m input.nei --flip -o flipped_mesh.nei
```

### **Add Symmetric Mesh Relative to the Equator**

Add the symmetric mesh relative to the equator:

```bash
mesh-editor -m input.nei --symetric -o symmetric_mesh.nei
```

### **Combine Projection and Flip**

Project the mesh and flip the north-south axis:

```bash
mesh-editor -m input.nei --proj --flip -o projected_flipped_mesh.nei
```

### **Combine All Transformations**

Project the mesh, flip the north-south axis, and add the symmetric mesh:

```bash
mesh-editor -m input.nei --proj --flip --symetric -o final_mesh.nei
```

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## Environment Variables

`mesh-editor` does not explicitly use environment variables. However, it may inherit standard system environment variables for file handling and debugging.

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## Notes

1. **Input File:**
  - The input mesh file **must** be in `.nei` format.
  - The `-m` option is **mandatory**. If not provided, the tool will exit with an error.
2. **Output File:**
  - If no output filename is specified (`-o`), the default `mesh-editor.nei` will be used.
3. **Transformations:**
  - The `--proj`, `--flip`, and `--symetric` options can be combined to apply multiple transformations in sequence.
  - The order of transformations matters. For example, flipping the mesh before projecting it may yield different results than projecting first and then flipping.
4. **Deprecated Options:**
  - Avoid using deprecated options, as they may be removed in future versions.

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## See Also

- [`mesh-doctor`](https://www.comodo-ocean.fr/) for more advanced mesh operations