> For the complete documentation index, see [llms.txt](https://docs.multiset.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.multiset.ai/webxr-sdk/api-reference/mapanchor.md).

# MapAnchor

```typescript
import { MapAnchor } from '@multisetai/vps/needle';
```

A Needle Engine `Behaviour` that applies VPS localization to a GameObject. After a successful localization, it transforms the object to the correct world position using the map-to-world matrix. `MapAnchor` is detected and wired automatically by `MultisetVPS` at startup.

### Inspector Fields

| Field                | Type            | Default        | Description                                                                                                                                         |
| -------------------- | --------------- | -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
| `offset`             | `THREE.Vector3` | `(0, 0, 0)`    | Position offset from the map origin in metres                                                                                                       |
| `matchOrientation`   | `boolean`       | `true`         | Align the object's rotation to the map orientation                                                                                                  |
| `rotationOffset`     | `THREE.Euler`   | `(0°, 0°, 0°)` | Additional rotation applied after `matchOrientation`. Only takes effect when `matchOrientation` is `true`.                                          |
| `hideUntilLocalized` | `boolean`       | `true`         | Keep the object invisible until the first successful localization and re-hide it when the session ends                                              |
| `isRightHanded`      | `boolean`       | `false`        | Set `true` if entering Three.js (right-handed) coordinates. Leave `false` for Unity (left-handed) coordinates — `MapAnchor` converts automatically. |

### Coordinate Handedness

Needle Engine uses Three.js coordinates (right-handed, Y-up). Unity uses a left-handed coordinate system. `MapAnchor` converts automatically when `isRightHanded` is `false`:

* The X component of `offset` is negated
* The Y and Z components of `rotationOffset` are negated

Set `isRightHanded: true` only if you are entering coordinates from a Three.js source (such as a previous localization result).

### Hiding Behavior

When `hideUntilLocalized` is `true`, the entire GameObject is hidden until the first localization. Because Needle Engine skips `start()` on invisible GameObjects, any sibling component that must run before localization should be placed on a separate always-visible GameObject.

### Public Methods

| Method                                                                           | Description                                                                                                                  |
| -------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- |
| `connectAdapter(adapter: NeedleAdapter)`                                         | Wire this anchor to an adapter. Called automatically by `MultisetVPS` for scene-placed anchors. Safe to call multiple times. |
| `applyLocalization(result: ILocalizeAndMapDetails, worldFromMap: THREE.Matrix4)` | Apply a localization result directly. Useful for testing or replaying a saved result.                                        |

### Needle Lifecycle

| Method        | Called when                                              |
| ------------- | -------------------------------------------------------- |
| `awake()`     | Sets `visible = false` if `hideUntilLocalized` is `true` |
| `onDestroy()` | Removes all registered listeners to prevent memory leaks |

### Runtime Instantiation

When a `MapAnchor` is instantiated at runtime (after `MultisetVPS.start()` has already run), call `registerAnchor` on the adapter to wire it up:

```typescript
import { instantiate } from '@needle-tools/engine';
import { MapAnchor } from '@multisetai/vps/needle';

const instance = instantiate(myPrefab);
const anchor = instance.getComponent(MapAnchor);

if (anchor && vps.adapter) {
  vps.adapter.registerAnchor(anchor);
  // If a localization already happened, the anchor is positioned immediately
}
```


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