Create anchors with ARCore for Jetpack XR

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An Anchor describes a fixed location and orientation in the real world. Attaching an object to an anchor helps objects appear realistically placed in the real world.

Create an ARCore for Jetpack XR session

Create anchors through an ARCore for Jetpack XR session. See Understand a Session's lifecycle to obtain a Session.

Configure the Session

Creating and loading anchors does not require the session to be configured. However, anchor persistence is not enabled by default on XR sessions. To persist and load anchors, configure the session:

val newConfig = session.config.copy(
    anchorPersistence = Config.AnchorPersistenceMode.Enabled,
)
when (val result = session.configure(newConfig)) {
    is SessionConfigureConfigurationNotSupported ->
        TODO(/* Some combinations of configurations are not valid. Handle this failure case. */)
    is SessionConfigurePermissionsNotGranted ->
        TODO(/* The required permissions in result.permissions have not been granted. */)
    is SessionConfigureSuccess -> TODO(/* Success! */)
}
Anchors.kt

Anchor content to a fixed location in space

An anchor is created using a Pose, which can be interpreted relative to an existing Trackable or not.

Create an anchor relative to a Trackable

When an anchor is created relative to a Trackable, such as a Plane, which makes the anchor follow the attached Trackable when it moves through space.

when (val result = trackable.createAnchor(pose)) {
    is AnchorCreateSuccess -> { /* anchor stored in `result.anchor`. */ }
    else -> { /* handle failure */ }
}
Anchors.kt

Create an anchor without a Trackable

To create an anchor that isn't attached to a Trackable:

when (val result = Anchor.create(session, pose)) {
    is AnchorCreateSuccess -> { /* anchor stored in `result.anchor`. */ }
    else -> { /* handle failure */ }
}
Anchors.kt

Attach an entity to an anchor

To render a model at this location, create a GltfModel and set its parent to an AnchorEntity.

AnchorEntity.create(session, anchor).apply {
    setParent(session.scene.activitySpace)
    addChild(entity)
}
Anchors.kt

Understand TrackingState

Each Trackable has a TrackingState that should be checked before being used. A Trackable that has a TrackableState of Tracking has its Pose actively updated by the system. A Trackable that is Paused may become Tracking in the future, whereas one that is Stopped will never become Tracking.

Persist an Anchor throughout sessions

An anchor that is not persisted disappears after a session is destroyed. By persisting an anchor, your app remembers that anchor's position in its private app data. This anchor can be retrieved in a subsequent session and is anchored in the same location in the world.

To persist an anchor, use Anchor.persist() as shown here:

val uuid = anchor.persist()
AnchorPersistence.kt

Your app can retrieve the anchor by using the UUID in a future session:

when (val result = Anchor.load(session, uuid)) {
    is AnchorCreateSuccess -> {
        // Loading was successful. The anchor is stored in result.anchor.
    }
    else -> {
        // handle failure
    }
}
AnchorPersistence.kt

When you don't need an anchor anymore, call unpersist(). This removes the anchor from your app's storage and makes the given UUID unretrievable for calls to Anchor.load().

Anchor.unpersist(session, uuid)
AnchorPersistence.kt

Your app can also request a list of all anchors that have been persisted that are still present in your app's storage:

val uuids = Anchor.getPersistedAnchorUuids(session)
AnchorPersistence.kt