Virtual Reality devices attach to the head (head mounted device or HMD) of a user and effectively puts a screen in front of the user’s eyes and using through electronic sensors, when a user turns their head in the real world, their virtual self’s head moves which creates the illusion that you are inside the virtual world. For a user to then interact with the virtual environment other than moving their head or using a traditional controller, like a keyboard, then their movements need to be tracked. A tracking system is used to track a user’s movements. In VR it is common to use an outside in tracking system which is where a device external to the user looks in at the user as they experience VR, it then translates the user’s movements in to the VR simulation to allow the user to know where they are in the virtual environment and to interact. There are different variations of the outside in tracking system and the main ones are the Oculus Rift Infrared (IR) Camera version, and to some extent the Valve Corporations’, Steam VR system which uses multiples of IR Laser base stations.
Oculus Rift
The Oculus Rift uses a technique known as “Constellation Tracking” which uses an Infrared Camera IR (more cameras improve range and accuracy) that points in to the space that the user is in. On the users HMD and controllers there are IR LED’s that the camera detects and use to determine the orientation and position of the user. The image to the left is of an Oculus Rift headset, IR camera, and controller.
Valve – Steam VR
This approach is used in the HTC Vive and is actually a hybrid approach between outside in and inside out tracking. External to the user’s controllers and HMD are two small base stations that are mounted normally in the corners of the room. The bases stations are synced with each other and alternatively they emit a pulse of IR light and then a laser IR sweep. The controllers and HMD have IR sensor on them that detect the laser light and lasers sweeps and, depending on when each sensor detects the IR laser light, their position and rotation can be determined. In the image below you can see a Vive HMD, two controllers, and two base stations.
To aid development of virtual reality HTC have released a small Vive Tracker that can be attached to any object to turn the object in to a VR object. The tracker works the same as a Vive controller and its positioning and orientation can be determined to sub millimetre accuracy. With the tracker you can turn everyday objects into tracked VR device, e.g. baseball bats and tennis rackets.
As well as using the Vive tracker, designers can develop their own custom tracked objects. Triad Semi Conductors are a main supply of components used to determine position in Steam VR, they also supply the sensors to HTC Vive. Triad have developed a SteamVR Hardware Development kit to allow designers and engineers to rapidly prototype custom controllers and tracked objects. After using the HDK to prototype custom electronics board can be developed and integrated into any product.
References
Billinghurst, M. (2017, 03 31). What is Mixed reality? Retrieved from Startup Grind: https://medium.com/startup-grind/what-is-mixed-reality-60e5cc284330
Kishino, P. M. (1994). A taxonomy of mixed reality visual displays. IEICE Transactions of Information Systems, 15.
Letxter, R. (2016, 04 6). My brain did something crazy and totally new in virtual reality. Retrieved from Buisiness Insider UK: http://uk.businessinsider.com/virtual-reality-gave-me-depth-perception-2016-4?r=US&IR=T
Ram, G. (2016, 09 16). How can Augmented reality be usd in sport? Retrieved from Affinity VR: http://www.affinityvr.com/augmented-reality-in-sports/
