Vuforia Fusion

Vuforia Fusion is a set of technologies designed to provide the best possible AR experience on a wide range of devices.

Fusion solves the problem of fragmentation in AR-enabling technologies, including cameras, sensors, chipsets, and software frameworks such as ARKit and ARCore. It senses the capabilities of the underlying device and fuses them with Vuforia Engine features, allowing developers to rely on a single Vuforia Engine API for an optimal AR experience. Vuforia Fusion brings advanced Vuforia Engine features to devices that support ARKit and ARCore, in addition to other Android and iOS device models.

Features

Vuforia Fusion is used by several Vuforia Engine features such as:

  • Device Tracker - Providing six-degree-of-freedom Device Pose
  • Ground Plane - Allowing virtual content to be placed on horizontal planes in the environment
  • Extended Tracking - enabling extended tracking for all Vuforia target types

Fusion Technology Priority

The priority of technology used by Vuforia Fusion has been optimized to leverage the richest set of hardware/software enablers while also providing developers the widest possible device coverage. Refer to the image below for an illustration of how the Vuforia Engine leverages hardware and software enablers.

In practice, what the above diagram shows is that an AR experience created using the Vuforia Engine will attempt to use the top most technology and work its way downward dependent on what is available on the device during runtime.

For example, a Vuforia App running on an iPhone X, will automatically leverage ARKit for all features dependent on Vuforia Fusion. That same application running on an older iOS device - which does not support ARKit but has been calibrated by Vuforia - will automatically use Vuforia VISLAM for dependent features.

The same scenario applies for Android devices. For example, a Vuforia App running on a Google Pixel 2 XL will leverage ARCore. That same application on a device that does not support ARCore will use Vuforia VISLAM if the device has the required sensors and has been calibrated by Vuforia.

Due to addition of support for platform enablers, it is important that AR content, targets, and physical objects all have their coordinate scale in meters. Objects that do not have their scale set appropriately may not track well.

Devices

For a list of devices that support ARKit or ARCore, please refer to Apple's ARKit Site or Google's ARCore Page.

For a list of recommended devices for use with Vuforia Engine, refer to Vuforia Engine Recommended Devices.

Older Devices and Overheating

In an effort to offer developers access to the broadest range of devices, the Vuforia Engine supports various older devices. Developers targeting older devices should be aware that these devices may not always have the hardware specifications required to sustain augmented reality experiences for long periods of time. Therefore, developers targeting such devices are encouraged to design shorter experiences. Running augmented reality experiences on such devices for prolonged periods can cause the device to overheat and/or battery drain.

There are several safeguards in devices to prevent damage to the device or injury to users.  One such safeguard is that the speed of the CPU and/or GPU are throttled in order to prevent the heat to cause permanent damage. When the CPU and/or GPU is throttled, augmented reality experiences may not behave as expected. For instance, augmentations may fail to be properly anchored to the environment or objects.

VISLAM Behavior

Visual-Inertial Simultaneous Localization And Mapping (VISLAM) is an algorithm implemented by Vuforia combining the benefits of Visual-Inertial Odometry (VIO) and Simultaneous Localization And Mapping (SLAM). Vuforia VISLAM has several benefits:

  • Works better in low-feature environments compared to SLAM based tracking,
  • Provides an estimate of the scale of the world (i.e., the DeviceTracker motion estimate will correspond to the real world motion), and
  • Provides robustness to recover when tracking is lost completely over VIO solutions.

When using Ground Plane, Vuforia Engine's VISLAM system will attempt to estimate the distance between the camera and the Ground Plane. To provide a smooth end-user-experience, Vuforia Engine will use the initial hints to scale based on height to the floor provided via developer API. The default of this hint is 1.4 meters - the average height of an adult holding a device in their hands. In some cases, you can see the scale-estimation at work in the initialization phase of your app when the augmentation is corrected in apparent size when placed onto the Ground Plane.

Fusion APIs

In some edge-cases developers may want to have tighter control over which Fusion Provider is used by the Vuforia Engine. The following APIs are available to change the priority order of the Fusion Providers.

The Vuforia::setAllowedFusionProviders (DeviceTracker.FusionMode in Unity) API takes a bitwise combination of the values as described below.

Fully automated provider selection

  • FUSION_PROVIDER_ALL - Vuforia Engine will select the best Fusion provider automatically. This is the default setting and should be used for most use-cases requiring Positional Device Tracker. Fusion Providers are prioritized as described above (platform enablers first, next is VISLAM then SLAM).

Enforcement of specific provider

  • FUSION_PROVIDER_PLATFORM_SENSOR_FUSION - Forces only platform enablers such as ARKit and ARCore. If none is available Vuforia::init() will fail.
  • FUSION_PROVIDER_VUFORIA_SENSOR_FUSION - Forces only Vuforia sensor fusion (VISLAM) technology only. If device was not calibrated by Vuforia, the Vuforia::init() call will fail.
  • FUSION_PROVIDER_VUFORIA_VISION_ONLY - Forces visual SLAM technology only without the use of sensors. Shall succeed on all devices, performance identical to Extended Tracking behavior in Vuforia Engine versions prior to SDK 7.0. No Anchors are supported with this Fusion provider.

In cases where the parameter flag does not modify the FUSION_PROVIDER_PLATFORM_SENSOR_FUSION bitwise value, the setAllowedFusionProvider can be set after Vuforia Engine initializes but before any trackers are initialized. In cases where the flag does modify FUSION_PROVIDER_PLATFORM_SENSOR_FUSION, the setAllowedFusionProvider must be set before Vuforia initializes.

Query

In the situation where you need to determine what is the current active Fusion provider, use the getActiveFusionProvider()(VuforiaRuntimeUtilities.GetActiveFusionProvider() in Unity) function. This call returns a specific value indicating what Fusion provider is being actively used by the Vuforia Engine. The return value is one of the listed items above in the Enforcement of specific provider section.

Continued AR Experiences

Vuforia offers developers a toolset to manage and create AR sessions that are sustained over application interrupts or pauses. By using the DeviceTrackableResult and its reported states, you can regain tracking of all Vuforia targets upon resuming the AR session. See Best Practices for Continued AR Experiences page for detailed information on application continuity and DeviceTracker states that are suitable for Vuforia Fusion platforms.

Relocalization

Relocalization allows a tracking system to recover tracking results after a short failure, without restarting the experience, by covering small gaps during the tracking function.

To determine whether Vuforia Engine is attempting to relocalize, refer to the DeviceTracker.getStatus() and DeviceTracker.getStatusInformation() functions.

In Vuforia Engine, relocalization behavior is highly dependent on the active Fusion Provider during a session.

When tracking is lost and getActiveFusionProvider() returns FUSION_PROVIDER_VUFORIA_VISION_ONLY, then the tracking system resets itself if it detects a previously unseen target. In this situation, the system starts tracking the new target and recovers additional targets as they come into view.

When tracking is lost and getActiveFusionProvider() returns FUSION_PROVIDER_VUFORIA_SENSOR_FUSION or FUSION_PROVIDER_VUFORIA_VISION_ONLY, then augmentations may not appear where expected. In this situation, getStatus() returns LIMITED. To help the system recover and continue the experience, instruct the user to point the device back to a previously viewed target or location, depending on the nature of the experience.

For more information on tracking state, refer to the Interpreting Tracking State API Results

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