Image Tracking

Image tracking functionality is implemented in projects using AR Foundation.

Requirements

• Requires Play For Dream MR device
• OS version 3.1.0 or higher

Usage Instructions

Below are basic instructions for using image tracking. For detailed documentation, refer to Unity's official AR Foundation Image Tracking documentation.

Configuring Image Library

Creating Reference Image Library

Adding Images to Reference Image Library

1. Open the Reference Image Library asset in the Inspector window
2. Click the Add Image button to add images to the library
3. In the image preview box, click "Select" to open the image browser
4. Choose relevant images from the dropdown list (repeat for each image)

Image Tracking Management Component

Enabling Image Tracking

To enable image tracking:

1. Add the AR Tracked Image Manager component to your XR Origin GameObject
2. If your scene doesn't contain an XR Origin GameObject, follow Unity's scene setup instructions first

Performance Note: Disable the AR Tracked Image Manager component when image tracking isn't needed to improve application performance. On unsupported devices, the component will automatically disable itself during OnEnable.

Setting Reference Image Library

To detect images in the environment:

1. Select the AR Tracked Image Manager component in the Inspector window
2. Click the Serialized Library selector (⊙)
3. Choose your reference image library from the Assets folder

Image Tracking Prefab

When an image from the reference library is detected, this prefab will be instantiated. The manager ensures instantiated GameObjects contain an ARTrackedImage component. Access reference image data through ARTrackedImage.referenceImage.

Responding to Detected Images

Subscribe to the AR Tracked Image Manager's trackablesChanged event to receive notifications when images are added, updated, or removed:

[SerializeField]
ARTrackedImageManager m_ImageManager;

void OnEnable() => m_ImageManager.trackablesChanged.AddListener(OnChanged);

void OnDisable() => m_ImageManager.trackablesChanged.RemoveListener(OnChanged);

void OnChanged(ARTrackablesChangedEventArgs<ARTrackedImage> eventArgs)
{
    foreach (var newImage in eventArgs.added)
    {
        // Handle added event
    }

    foreach (var updatedImage in eventArgs.updated)
    {
        // Handle updated event
    }

    foreach (var removed in eventArgs.removed)
    {
        // Handle removed event
        TrackableId removedImageTrackableId = removed.Key;
        ARTrackedImage removedImage = removed.Value;
    }
}

Image Tracking Component

The ARTrackedImage component is a trackable object containing data associated with detected 2D images. When the device detects a 2D image from the reference library in the environment, the AR Tracked Image Manager creates an ARTrackedImage.

Key properties include:

• name: Identifier of recognized image
• trackingState: Current tracking status
• size: Physical dimensions of detected image
• pose: Position and rotation in world space