> ## Documentation Index
> Fetch the complete documentation index at: https://dadd.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# useBodyMeshes

> Hook that returns Three.js meshes for a MuJoCo body

Returns the `THREE.Mesh[]` array for a given MuJoCo body ID. This is the low-level primitive for building custom selection visuals, outlines, postprocessing effects, or any logic that needs direct access to the meshes belonging to a body.

## Signature

```tsx theme={null}
useBodyMeshes(bodyId: number | null): THREE.Mesh[]
```

## Usage

```tsx theme={null}
import { useBodyMeshes } from "mujoco-react";

function CustomOutline({ bodyId }: { bodyId: number | null }) {
  const meshes = useBodyMeshes(bodyId);

  useEffect(() => {
    // Apply a custom outline effect to each mesh
    meshes.forEach((mesh) => {
      mesh.layers.enable(1); // e.g. assign to an outline layer
    });
    return () => {
      meshes.forEach((mesh) => {
        mesh.layers.disable(1);
      });
    };
  }, [meshes]);

  return null;
}
```

### Custom Selection Visuals

Because `useBodyMeshes` gives you raw mesh references, you can implement any visual effect:

```tsx theme={null}
import { useBodyMeshes } from "mujoco-react";
import { useFrame } from "@react-three/fiber";

function PulsingHighlight({ bodyId }: { bodyId: number }) {
  const meshes = useBodyMeshes(bodyId);

  useFrame(({ clock }) => {
    const intensity = (Math.sin(clock.elapsedTime * 4) + 1) / 2;
    meshes.forEach((mesh) => {
      const mat = mesh.material as THREE.MeshStandardMaterial;
      mat.emissiveIntensity = intensity * 0.5;
      mat.emissive.set("#ff8800");
    });
  });

  return null;
}
```

### Postprocessing

Pair with `@react-three/postprocessing` to apply per-body effects:

```tsx theme={null}
import { useBodyMeshes } from "mujoco-react";
import { Selection, Select, EffectComposer, Outline } from "@react-three/postprocessing";

function OutlineSelectedBody({ bodyId }: { bodyId: number | null }) {
  const meshes = useBodyMeshes(bodyId);

  return (
    <Selection>
      <EffectComposer>
        <Outline blur edgeStrength={3} />
      </EffectComposer>
      {meshes.map((mesh, i) => (
        <Select key={i} enabled>
          <primitive object={mesh} />
        </Select>
      ))}
    </Selection>
  );
}
```

## Parameters

| Parameter | Type             | Default | Description                                               |
| --------- | ---------------- | ------- | --------------------------------------------------------- |
| `bodyId`  | `number \| null` | --      | ID of the MuJoCo body. Pass `null` to get an empty array. |

## Returns

| Type           | Description                                                                                               |
| -------------- | --------------------------------------------------------------------------------------------------------- |
| `THREE.Mesh[]` | Array of Three.js meshes belonging to the body. Empty array if `bodyId` is `null` or no meshes are found. |

## How It Works

Traverses the R3F scene graph and collects all meshes whose `userData.bodyID` matches the given `bodyId`. The `<SceneRenderer>` component sets `userData.bodyID` on every mesh it creates, so this hook works with any standard mujoco-react scene.

## Related

* [`useSelectionHighlight`](/hooks/use-selection-highlight) -- convenience hook built on `useBodyMeshes` for emissive highlights