Hololight Stream provides functionality to scan QR Codes in the physical environment and receive the information within Unity to be processed. This feature is supported on HoloLens 2, iOS/iPadOS and Magic Leap 2 clients.
This functionality has been implemented as a tracked AR Subsystem called XRQrCodeTrackingSubsystem. This follows similar implementations to other Unity subsystems, such as image tracking and anchors.
To ease usage, an AR Foundation manager has been provided called ARQrCodeTrackerManager which interfaces with the underlying subsystem for tracking QR codes.
The QR code tracking manager creates GameObjects for each detected QR code in the environment. Once detected, the QR Code information can be read and processed. This manager can be found at the namespace HoloLight.Isar.ARFoundation.
Subscribe to the ARQrCodeTrackerManager's trackedQrCodesChanged event to be notified whenever a QR code is added (i.e., first detected), updated, or removed:
[SerializeField]
ARQrCodeTrackerManager m_QrCodeTrackerManager;
void OnEnable() => m_QrCodeTrackerManager.trackedQrCodesChanged += OnChanged;
void OnDisable() => m_QrCodeTrackerManager.trackedQrCodesChanged -= OnChanged;
void OnChanged(ARQrCodeChangedEventArgs eventArgs)
{
foreach (var newQrCode in eventArgs.added)
{
// Handle added event
}
foreach (var updatedQrCode in eventArgs.updated)
{
// Handle updated event
}
foreach (var removedQrCode in eventArgs.removed)
{
// Handle removed event
}
}
You can also get all the currently tracked QR codes with the ARQrCodeTrackerManager's trackables property. This acts like an IEnumerable collection, so you can use it in a foreach statement:
void ListAllQrCodes()
{
Debug.Log(
$"There are {m_QrCodeTrackingManager.trackables.count} QR codes being tracked.");
foreach (var trackedQrCode in m_QrCodeTrackingManager.trackables)
{
Debug.Log($"QR Code: {trackedQrCode.trackableId} is at " +
$"{trackedQrCode.transform.position}");
}
}
Or access a specific image by its TrackableId:
ARQrCode GetQrCodeAt(TrackableId trackableId)
{
return m_QrCodeTrackingManager.trackables[trackableId];
}
The ARQrCode class contains a byte array property called data. This contains the information which has been read from the QR code. This data can be used for carrying out specific logic based on the type of QR code.
This data is specific to the QR code version and has to be read correctly. To aid in this, a helper function is provided with the ARQrCode class called ReadData. This function will convert the QR code data from a byte array to a string for usage.
Note, the ReadData function assumes that the QR code data read was in UTF8 encoding format. If this is not the case, custom parsing will be required.
The ARQrCodeTrackingManager has a "QR Code Prefab" field; however, this is not intended for content. When a QR code is detected, ARFoundation will create a new GameObject to represent it.
If "Qr Code Prefab" is null, then ARFoundation simply creates a GameObject with an ARQrCode component on it. However, if you want every tracked QR code to also include additional components, you can provide a prefab for ARFoundation to instantiate for each detected QR code. In other words, the purpose of the prefab field is to extend the default behavior of tracked QR codes; it is not the recommended way to place content in the world.
If you would like to instantiate content at the pose of the detected QR codes and have its pose updated automatically, then you should parent your content to the ARQrCode.
The ARQrCodeTrackingManager has an enabled property which can be set to enable/disable the QR code tracking. When finished tracking, it is recommended to set the enabled property to false to provide better performance.
See Unity's AR Foundation Trackable Managers Documentation for more information on usage of AR Foundation trackable managers.