Two years ago, Google introduced Cloud Anchors in ARCore 1.2 to enable collaborative AR experiences across devices. In its latest release, ARCore removes a limitation in Cloud Anchors by providing support for full persistence. Additionally, ARCore 1.20 integrates with Google Earth to make it easier to find AR content.
Cloud Anchors make it possible to create shared augmented reality experiences, such as drawing on a wall or playing a game along with other people. In other words, different users can participate in the same experience using different devices.
Cloud anchors enable two different operations: creating a new anchor by sending it to Google Cloud Anchor service along with its position, and getting all anchors belonging to the same room.
One feature that was missing from the initial release of Cloud Anchors was persistence. As a matter of fact, Cloud Anchors inevitably need some form of Cloud storage, but until now they were only persisted for one day. This limitation made Cloud Anchors suitable for local multiplayer gaming but did not allow users to create non-ephemeral experiences they could return to whenever they need to. Enabling this opens up entirely new possibilities. For example, Google explains, you can virtually create an evolving natural habitat in your home and return to it after some time to see how it has changed. Another example, is an AR tour guide app that can virtually take you to certain locations and show you AR content. Yet another case mentioned by Google is home design, whereby you place virtual furniture in your home with the possibility of visiting and modifying the scene as many times as needed until satisfied by the result.
To use Cloud Anchors in your app, you will need to enable them first. Then, for each anchor you would like to persist for longer than the default 24 hours, you can call hostCloudAnchorWithTtl and specify the anchor time to live between one and 365 days. You can also extend the lifetime of an already hosted anchor. In order to host Cloud Anchors, you need to use keyless authentication based on OAuth.
Make sure also you check API quotas for anchor host and resolve requests and take into consideration increased levels of battery and memory usage due to higher network usage and CPU utilization before adopting this technology.
As a final note, ARCore 1.20 also introduces Earth Cloud Anchors as a preview developers can apply to. Based on global localization, a technology aimed to improve the accuracy of the "blue dot" that indicates your current position and orientation in Google Maps, this feature is meant to improve the ways people can discover AR experiences attached to physical places across the world.