Positional Tracking

Meta: Positional tracking is part of the many technologies that make virtual reality possible. To help you understand VR better, here’s a fundamental guide to the different types of positional tracking.

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A Guide To 5 Types Of Positional Tracking

Positional tracking is a technology that combines hardware and software so that the device that you use in virtual reality (VR) can estimate its position depending on the environment that surrounds it. It allows detection of an absolute position and is an essential VR technology that is constantly improving with accuracy and performance. Here’s a list of five types of positional tracking that you can get familiar with.

Inside-Out Tracking

This positional tracking type is commonly used when you want to track the position of motion controller accessories and head-mounted displays for the purposes of virtual reality. The camera is actually located on the particular device that is being tracked, and is commonly used where the device wants to determine any changes in position made according to the environment. As the headset moves, sensors make adjustments so that the virtual environment will be able to respond to that change in real-time. Its advantages include a “cableless” experience: freeing up users from cables and external hardware. This kind of tracking requires higher computational power; potentially increasing latency and reducing quality.

Outside-In Tracking

This is usually referred to as a method of optical tracking where cameras, or other sensors and accessories are placed in a stationary position so that it can be oriented towards the headset, or the tracked object. (e.g. Vive “Lighthouses”) There are intersecting visual ranges defined in a designated area so that the camera can track the movement accordingly. In other words, the object is observed using the tracking device from the outside. Infrared markers are commonly used to detect the type of light in the visible light spectrum. With the external lighthouses being powered individually, it achieves a low latency system. However, occlusion and viewing ranges of the sensors require you to have a decently sized playspace. 

Markerless Tracking

This method, as the name implies, does not rely on the use of specific optical markers, thus making it a more flexible method over its marker-based counterparts. Markerless Tracking relies on the method of observing its environment to calculate the position and orientation of the camera. Users can walk freely in a space or even in a new environment while still receiving the positional feedback. This implies that the applicability range is also expanded. Factors that may affect markerless tracking can be textural or geometric shapes of objects, backgrounds, reflections, and light positions.

Markerless Inside-Out Tracking

This type of markerless tracking provides users with increased mobility for its users, while the computer calculates the headset's position using depth, acceleration, and other signals, without using the so-called fixed point of reference. This system prevents any occlusion too, which is a common problem with marker-based tracking. Markerless inside-out positional tracking also doesn’t need the use of external cables and sensors, but rather depends on the use of a light emitter.

Markerless Outside-In Tracking

This is one of the technologies already available to consumers even before the use of VR devices. Among non-VR systems that used this technology is Playstation's EyeToy: released in 2003, and that of Kinect from Xbox that was released in 2010. This system allowed for mounting of cameras in the environment, which will then be aimed at the user. Movements of the user are tracked without depending on any type of hardware or markers.

All in all, these positional tracking types are what allows VR to function in accurate ways according to your real-world movement. Hopefully this article will enable you to pinpoint which technology will work to your advantage while enjoying VR.