Motion Tracking in VR

Posted by Abhijeet Naik at 2017-08-10 10:25:16

Motion Tracking in VR

In my last article we discussed how Virtual Reality uses Hand Tracking Tech to increase sense of immersion and presence in a virtual environment. But, Hand tracking is not just one of the human senses that increases immersion. Researchers, start-ups and HMD manufactures have found a way to virtually teleport human body in Virtual Reality and that is accomplished by using Motion Tracking Tech in Virtual Reality. 

Before we dive deep into motion tracking in VR, its important to understand the free movement of a rigid body in three dimensional space which is also known as 6DOF or 6 Degree Of Freedom. Any motion tracking system should be able to measure these 6 Degree Of Freedom. There are mainly two types of motion tracking technlogies optical and non optical. 

Optical Motion Tracking In VR mainly uses multiple motion sensor cameras to track precise body movement. These motion sensor cameras generates multiple images to traingulate the 3d position of the subject. In Oculus Rift, in a conference it was demonstrated that using 3 motion sensor one can achieve occulusion free room scale experience. But, as these are image data, sometimes with low light, the error rate of tracking device goes up and it sometimes breaks the immersion of the virtual environment. So, there is another type of tracking called as non optical tracking device which increases the immersion and decreases the tracking device error rate. 

A Non Optical Motion Tracking usually consists of inertial sensors, gyroscope, accelerometer, and other sensor based tracking. These sensor data are fed into a algorithm which helps further determine precise position and coordinates like one used in head tracking. Head tracking in mobile VR is mostly done using the combination of gyroscope and the device which helps the system to understand where the user is currently looking and based on the data it turns the virtual camera around in the virtual world. 

In Virtual Reality, Optical Motion Tracking and Non Optical Motion Tracking are mostly combined to achieve a low error rate tracking, like in HTC Vive they are using a tracker called as Vive Tracker. This tracker contains a gyroscope and Accelerometer which helps a user to add real world object, its transforms and its precise position in real world. This, helps user to immerse even more and gives a chance to the developer to create highly immersive Virtual Reality experiences. 

That said, motion tracking tech is still evolving when it comes to be used in conjunction with Virtual Reality Headsets. There is still some latency, because the system has to perform complex computation on real time basis and on each frame. If the latency between the Tracking Device and the system is too high it can break the immersion. 

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