> For the complete documentation index, see [llms.txt](https://studio-docs.sandbox.game/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://studio-docs.sandbox.game/the-editor/how-to-set-collision-and-navmesh-on-mesh-models.md).

# How to set collision and navmesh on mesh models

Physics and navigation are two different jobs on the same Model Mesh Node.

**Physics** is what the player pawn bumps into and stands on. **Navmesh** is the walkable map AI uses. A decorative kit piece can block the pawn, sit outside the navmesh, or both.

A dragged `.glb` starts with physics **on**: motion `static`, profile `BlockAll`, collision mesh `convexHull`. Change those when the piece is only visual, or when the hull is the wrong shape.

What those fields mean, and what **Rapier** is when the console names it: [What physics and Rapier mean in Sandbox Studio](/the-editor/what-physics-and-rapier-mean.md).

The player’s visible model is the opposite: physics **off** on the `.glb`, collision on a hidden capsule. See [How to use a character pawn](/the-editor/how-to-use-a-character-pawn.md).

## Physics vs navmesh vs look

| Job                   | Inspector fields                                     | Typical kit piece                                                               |
| --------------------- | ---------------------------------------------------- | ------------------------------------------------------------------------------- |
| Pawn walks and slides | Physics enabled, motion `static`, profile `BlockAll` | Ground and solid modules                                                        |
| AI paths              | `navigationGeometryRole`                             | Ground `walkable`; solid modules `obstacle`; banners and sky dressing `exclude` |
| What you see          | `modelUrl`, **Model Material**                       | Independent of physics and nav                                                  |

`navigationGeometryRole` values verified in the editor and engine:

| Role       | Meaning                                 |
| ---------- | --------------------------------------- |
| `walkable` | This mesh is ground the navmesh can use |
| `obstacle` | This mesh blocks the navmesh            |
| `exclude`  | Ignore this mesh when baking nav        |

Collision mesh type on a Model Mesh Node (values seen in the Inspector):

| Type          | When to use                                                                  |
| ------------- | ---------------------------------------------------------------------------- |
| `convexHull`  | Default after a drag. Fine for simple ground and chunky props                |
| `boundingBox` | A cheaper box around the mesh. Use when a hull is too tight or too expensive |

{% hint style="info" %}
*NOTE: Physics on the visual character `.glb` makes the body a wall. Leave physics off on that node. Keep collision on the capsule.*
{% endhint %}

{% stepper %}
{% step %}

## Select the Model Mesh Node

Select the mesh that holds `modelUrl`. If the Outliner shows a Model Mesh Actor parent, select the **Model Mesh Node** child. See [How to kitbash a level from mesh models](/the-editor/how-to-kitbash-a-level-from-mesh-models.md).
{% endstep %}

{% step %}

## Set physics for the pawn

For ground and solid scenery, leave physics enabled, motion `static`, profile `BlockAll`.

For a mesh that should not block anyone (a card, a distant backdrop), turn physics **off**.

Pick collision mesh type: `convexHull` or `boundingBox`. Enter Play and walk the pawn into the piece. If you snag on invisible corners, switch type or turn physics off and use a simpler Mesh Node collider as a child.
{% endstep %}

{% step %}

## Set the navigation role

Set `navigationGeometryRole`:

* Ground you want AI to cross → `walkable`
* Buildings and blockers AI should path around → `obstacle`
* Dressing that must not punch holes in the bake → `exclude`
  {% endstep %}

{% step %}

## Generate or refresh the navmesh

The scene can store a `.navmesh` file and a `.navmsettings.json` next to the `.genesys-scene`. Generation settings include `cellSize`, `cellHeight`, `walkableSlopeAngle`, `walkableRadius`, and related numeric fields.

Ask the agent to generate the navmesh, toggle debug view, and export or import the `.navmesh` through [Sandbox Studio MCP](/working-efficiently-with-ai/set-up-and-use-sandbox-studio-mcp.md). MCP can generate, clear, import, export, set settings, and toggle debug.

Turn debug on, look at the walkable surface, then turn it off. If AI walks through a module, that mesh is probably `exclude` or physics-only. If AI will not cross a platform, that mesh is probably not `walkable`.
{% endstep %}
{% endstepper %}

## Common mistakes

| What went wrong                                | What to do                                                                                |
| ---------------------------------------------- | ----------------------------------------------------------------------------------------- |
| Dragged a character `.glb` and got stuck on it | Physics off on the visual node. Player collision is the pawn capsule.                     |
| AI walks through a solid kit piece             | Set `navigationGeometryRole` to `obstacle` and generate the navmesh again.                |
| Navmesh eats a backdrop or particle mesh       | Set that node to `exclude`.                                                               |
| Pawn falls through the ground                  | Physics on, `static`, `BlockAll`, on the ground mesh. Place Player Start on that surface. |

## What You've Done

You can tell pawn collision from AI nav, set hull or box on a Model Mesh Node, and bake a navmesh the agent can debug. Next: [How to use a character pawn](/the-editor/how-to-use-a-character-pawn.md), or [How to Set Up a Prefab](/the-editor/how-to-set-up-a-prefab.md) if the collider and mesh should travel together.


---

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