Cloud Anchors developer guide for ARCore Extensions targeting Android

Learn how to use Cloud Anchors in your own apps.

Prerequisites

Make sure that you understand fundamental AR concepts and how to configure an ARCore session before proceeding.

If you are new to Cloud Anchors, make sure that you understand how anchors and Cloud Anchors work.

Enable the ARCore API

Before using Cloud Anchors in your app, you must first enable the ARCore API in a new or existing Google Cloud Platform project. This service is responsible for hosting, storing, and resolving Cloud Anchors.

Authorize your app to call the ARCore API

You must authorize your app to call the ARCore API to host and resolve Cloud Anchors. Apps that host and resolve Cloud Anchors with a TTL greater than 1 day must use keyless authorization.

Enable Cloud Anchors functionality in your app

After authorizing your app to call the ARCore API, you must enable Cloud Anchors functionality in your app.

1. Navigate to Edit > Project Settings > XR Plug-In Management > ARCore Extensions.
2. Under Optional Features, select Cloud Anchors.

Enable Cloud Anchor capabilities in the session configuration

Once Cloud Anchors functionality has been enabled in your app, enable Cloud Anchors capabilities in your app’s AR session configuration so that it can communicate with the ARCore API:

1. Ensure that the project Assets folder contains an ARCoreExtensionsConfig scriptable object. To create one, right-click in the Assets pane and select Create > XR > ARCore Extensions Config.

2. Select the ARCoreExtensionsConfig scriptable object in your Assets folder and set the Cloud Anchor Mode to Enabled.

   

3. Configure the ARCore Extensions game object to use the ARCoreExtensionsConfig configuration. In the Hierarchy pane, locate the ARCore Extensions game object you created when you initially set up ARCore Extensions, and connect the ARCore Extensions Config field to the ARCoreExtensionsConfig scriptable object in your Assets folder.

   

Host a Cloud Anchor

Hosting starts with a call to ARAnchorManager.HostCloudAnchorAsync(). ARCore will upload visual data, device poses, and the anchor pose to the ARCore API. The API then processes this information to construct a 3D feature map, ultimately returning a unique Cloud Anchor ID for the anchor to the device.

You can also extend the lifetime of a hosted anchor using the ARCore Cloud Anchor Management API.

Your app should follow these steps to complete hosting of a Cloud Anchor:

1. Call ARAnchorManager.HostCloudAnchorAsync().
2. Start a coroutine to wait until the Promise yields a result. See Coroutines in Unity for additional information.
3. Check the result state to determine if the operation succeeded, or interpret the error code if it failed.
4. Share the result Cloud Anchor ID with other clients, and use it to resolve the Cloud Anchor with ARAnchorManagerExtensions.ResolveCloudAnchorAsync().

Check the mapping quality of feature points

ARCoreExtensions.FeatureMapQuality indicates the quality of feature points seen by ARCore in the preceding few seconds from a given camera pose. Cloud Anchors hosted using higher quality features are generally more accurately resolved. Use ARAnchorManagerExtensions.EstimateFeatureMapQualityForHosting() to obtain an estimation for the feature map quality for a given camera pose.

Value	Description
Insufficient	The quality of feature points identified from the pose in the preceding few seconds is low. This state indicates that ARCore will likely have more difficulty resolving the Cloud Anchor. Encourage the user to move the device so that the desired position of the Cloud Anchor that they wish to host can be viewed from different angles.
Sufficient	The quality of feature points identified from the pose in the preceding few seconds is likely sufficient for ARCore to successfully resolve a Cloud Anchor, although the accuracy of the resolved pose will likely be reduced. Encourage the user to move the device so that the desired position of the Cloud Anchor that they wish to host can be viewed from different angles.
Good	The quality of feature points identified from the pose in the preceding few seconds is likely sufficient for ARCore to successfully resolve a Cloud Anchor with a high degree of accuracy.

Resolve a previously hosted anchor

Call ARAnchorManagerExtensions.ResolveCloudAnchorAsync() to resolve a hosted Cloud Anchor. The ARCore API periodically compares visual features from the scene against the anchor’s 3D feature map to pinpoint the user's position and orientation relative to the anchor. When it finds a match, the API returns the pose of the hosted Cloud Anchor.

You can initiate resolves for multiple Cloud Anchors in sequence. Up to 40 concurrent Cloud Anchor operations can exist at a time.

Cancel an operation or remove a Cloud Anchor

ARCloudAnchor.OnDestroy() is automatically called when the ARCloudAnchor component is removed from the game object containing it. This will detach and release the underlying native Cloud Anchor object.

Check the result state of a Cloud Anchor operation

Use CloudAnchorState to check the result status of the hosting or resolving operation, including errors.

Value	Description
ErrorResolvingCloudIdNotFound	Resolving failed because the ARCore API could not find the provided Cloud Anchor ID.
ErrorHostingDatasetProcessingFailed	Hosting failed because the server could not successfully process the dataset for the given anchor. Try again after the device has gathered more data from the environment.
ErrorHostingServiceUnavailable	The ARCore API was unreachable. This can happen for a number of reasons. The device might be in airplane mode or may not have a working Internet connection. The request sent to the server might have timed out with no response. There might be a bad network connection, DNS unavailability, firewall issues, or anything else that might affect the device's ability to connect to the ARCore API.
ErrorInternal	A hosting or resolving task for this anchor finished with an internal error. The app should not attempt to recover from this error.
ErrorNotAuthorized	The app cannot communicate with the ARCore API because of invalid authorization. Check Project Settings > XR > ARCore Extensions for a valid authorization strategy.
ErrorResolvingPackageTooNew	The Cloud Anchor could not be resolved because the ARCore Extensions package used to resolve the Cloud Anchor is newer than, and incompatible with, the version being used to host it.
ErrorResolvingPackageTooOld	The Cloud Anchor could not be resolved because the ARCore Extensions package used to resolve the Cloud Anchor is older than, and incompatible with, the version being used to host it.
ErrorResourceExhausted	The application has exhausted the request quota allotted to the given Google Cloud project. You should request additional quota for the ARCore API for your project from the Google Developers Console.
Success	A hosting or resolving task for this anchor completed successfully.

API quotas for host and resolve requests

The ARCore API has the following quotas for request bandwidth:

Quota type	Maximum	Duration	Applies to
Number of anchors	unlimited	N/A	project
Anchor host requests	30	minute	IP address and project
Anchor resolve requests	300	minute	IP address and project

Best practices for a good user experience

Instruct users to do the following to ensure a good user experience on your app:

• Wait a few seconds after the session starts before attempting to host an anchor (by placing an object, etc.). This gives the tracking some time to stabilize.
• When selecting a location to host the anchor, try to find an area with visual features that are easily distinguishable from one another. For best results, avoid reflective surfaces or surfaces that lack visual features, such as blank white walls.

• Keep the camera trained on the center of interest and move the device around the center of interest to map the environment from different angles, maintaining roughly the same physical distance as you do so. This will help capture more visual data and make resolving more robust.

• Make sure that there is sufficient lighting in the real-life environment while hosting and resolving Cloud Anchors.

Deprecation policy

• Apps built with ARCore SDK 1.12.0 or higher are covered by the Cloud Anchor API deprecation policy.
• Apps built with ARCore SDK 1.11.0 or lower are unable to host or resolve Cloud Anchors due to the SDK's use of an older, deprecated ARCore API.

What's next

• Check out the ARCore Extensions for AR Foundation reference documentation for more ways to use ARCore in your app.