MapAnchor

Needle Engine component that positions a GameObject at a map-local coordinate after localization

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.

For a layout of several anchored objects, prefer MapSpace. One frame is positioned per localization and every child follows, so a child's local Transform position is its map coordinate. MapAnchor remains the right choice for a single object, for an object that must not inherit the map's rotation (matchOrientation: false), and for objects spawned at runtime.

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:

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
}