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OptiTrack, ART, and Other Positional Tracking Alternatives to SteamVR

April 21, 2023
by Ferhat Sen, Director, XR Technology Solutions, Varjo
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XR/VR generic

Positional tracking refers to a system in a VR/XR headset that determines its exact position. Tracking allows applications to synchronize your movements in the real world with those in the virtual environment in real time. Without proper tracking, if you try to lean or move your head’s position, the entire virtual world would move with your head’s movement because it would not be tracked. This would create an unrealistic virtual experience and even cause cybersickness.

There are several positional tracking providers on the market. While SteamVR tracking using base stations is the most well-known and widely used positional tracking method for headsets, it is not the only solution. Other solutions, such as ART and OptiTrack, are also available and can be a better fit in different kinds of VR/XR simulation scenarios.  

But what are the differences between the 3rd party positional tracking vendors supported on Varjo headsets, and what kind of use cases are they best suited for?  

 

VR Base Stations
Varjo headsets work together with SteamVR™ base stations manufactured by Valve.

SteamVR Tracking 

SteamVR tracking is often the best solution in scenarios where the person using the headset remains relatively stationary or only moves around in a limited space, such as a single room. It uses up to four SteamVR base stations to track your headset and optional controllers. The base stations only need to be connected to power outlets. 

As a fairly versatile solution, base-station tracking is suitable for many use cases where sub-millimeter tracking accuracy is not required. The main limitation of SteamVR tracking is that it is not suited for use cases requiring considerable movement (such as in-car tracking while the car is in motion) or larger spaces since the base stations have a maximum range of up to 7m x 7m meters (23 feet x 23 feet) with four base stations. The base stations are sensitive to physical movements, and they need to be stationary to function, and that’s why it is not a suitable solution for in-car or on-ship solutions.  

SteamVR tracking is the most inexpensive solution, and Varjo headsets have built-in support for SteamVR tracking. The only things you would need separately are the base stations and, optionally, controllers.  

For more information about setting up SteamVR tracking, see our setup guide.  

 

BMW mixed reality drive with Varjo XR-3 headset in WebSummit 2022
An example of an in-car tracking system developed by BMW using Varjo XR-3 and ART.

ART 

ART, or Advanced Realtime Tracking, is an optical motion tracking system for virtual and augmented reality. The most popular use cases for the ART system include automotive design, in-car tracking, cockpit integrations, and large-scale tracking. It is rather a grade tracking solution for use cases where tracking accuracy is important.  

Similarly, ART is well suited for in-car tracking because there are similar distance and space limitations and the need for wide-angle tracking. In addition, ART has good shock resistance, which is crucial when a car needs to be driven while the tracking is used. 

Large-scale tracking scenarios include virtual walkthroughs such as interior design, automotive design, factory tours, constructions, production line inspections, etc. These situations can often also have multiple users that need to interact and collaborate together, which might make simple base station setups like Steam VR challenging to use. 

Varjo has support for the ART tracking system through its third-party tracking plugin API. This means that you would need an ART marker attached to the headset and a plugin that either you develop or purchase from LP-Research.  

OptiTrack

 

OptiTrack
Image: ©OptiTrack

OptiTrack for VR is a wide area tracking system best suited for large spaces exceeding 30 meters by 30 meters (100 feet by 100 feet) where you need to track multiple users. A practical example of this would be multiplayer VR arcade games.  

OptiTrack uses cameras and reflective markers to track multiple objects, such as the headset, tools, hands, controllers, and even the full body of the users. There are two different kinds of OptiTrack solutions: active and passive.  

Passive tracking works by placing low-mass reflective markers on the tracked person or object. This keeps all the technology with the cameras and not on the subjects. Passive tracking requires that each object tracked has a spatially different marker cluster, so each object must be unique. The passive method is best suited for research VR, ground truth systems, and out-of-home experiences with just one or two sites.  

OptiTrack Active is best suited for larger-scale installations.  

Varjo supports the OptiTrack tracking system through its 3rd party tracking plugin API. This means that you would need an OptiTrack marker attached to the headset and a plugin that either you develop or purchase from LP-Research.  

 

 LP Research tracking
An example of Phiaro’s modular XR chassis using LP Research tracking.

LP-Research 

Life Performance Research offers two tracking plugins for Varjo headsets. LPVR-CAD, a location-based tracking solution, and LPVR-DUO, an in-vehicle tracking solution. These plugins enable you to use either ART or OptiTrack tracking systems with Varjo headsets.  

LPVR-CAD is a middleware solution that combines optical tracking information with inertial measurement data by using a predictive algorithm based on a head motion model. This allows the system to have very little latency, even in large spaces. It can be used together with ART or OptiTrack. Example use cases include automotive CAD and pre-production design inspection, location-based virtual reality entertainment, and interactive theater and art installations. 

LPVR-DUO is an in-car tracking system that fuses inertial measurement data using a special predictive algorithm based on a head motion model. It is a middleware solution that supports ART and OptiTrack.  

It is a solution for VR that enables headset manufacturers to create a state-of-the-art visualization pipeline customized to their product easily. The system also allows the flexible combination of multiple optical systems and inertial measurement units for combined position and orientation tracking. This enables the decoupling of the head motion of a user and the movement of a vehicle the user is riding in. This way, the interior of a car can be displayed as static relative to the user, while the scenery in the vehicle’s environment moves with vehicle motion.

 

Want to learn which tracking solution would best fit your VR/XR scenario? Reach out to our expert team to book a call.

 

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