# The Influence of Immersive Virtual Reality Systems on Online Social Application
## 3 Developing RVM-IVRSA
### Motion Tracking  
A very important function in functional layer is optical positioning of a head display and three points of two controllers, so as to achieve the capture of the user's head and hand movements, which is  
Figure 3: A virtual scene built in Unity3D. Figure 2: Main functions, network architecture, and underlying data classification of roaming, voice communication, motion capture immersive virtual reality social application (RVM-IVRSA). the basis of body language expression in a virtual space [23]. The HTC VIVE system includes the following components: VIVE HMD, two Lighthouse laser base stations, and two wireless controllers. The most traditional way to track head position with VR headsets is to use inertial sensors, but inertial sensors can only measure rotation (rotation around the XYZ triaxial axis, called the three degrees of freedom), not movement (along the XYZ triaxial axis, the other three degrees of freedom, collectively called the six degrees of freedom) [24]. In addition, inertia sensor error is relatively large if there is a need for more accurate and free tracking of head movement, or additionally a need for other location-tracking technology. Instead of the usual optical lens and mark point positioning system, the Lighthouse system used by HTC VIVE consists of two laser base stations: an infrared LED array in each base station, and an infrared laser transmitter with two rotating axes perpendicular to each other, with a rotation speed of 10 ms. The base station takes 20 ms as a cycle. At the beginning of a cycle, the infrared LED flashes. The rotating laser on the \(X\)-axis within 10 ms sweeps the user's free activity area. In the remaining 10 ms, the rotation laser of the \(Y\)-axis sweeps the user's free activity area, and the \(X\)-axis does not emit light [25; 26]. The Lighthouse base station valve has a number of light-sensitive sensors installed on its HMD, and the controller signal is synchronized after the base station's LED flashes, with light-sensitive sensors being able to measure the time it takes the \(X\)-axis laser and \(Y\)-axis laser to reach the sensor. This is exactly the time it takes for the \(X\)-axis and \(Y\)-axis lasers to go to this particular angle, and thus the \(X\)-axis and \(Y\)-axis angles of the sensor relative to the base station is known. The position of photosensitive sensors distributed on the head display and controller is also known, and thus the position of the head display and motion trajectory can be calculated by the position difference of each sensor. HTC VIVE's positioning system captures and maps spatial position and rotation of HMD and two controllers into virtual space [27]. The schematic diagram is shown in Figure 4.  
The screen of user using RVM-IVRSA is shown in Figure 5. What is displayed is the perspective of the user in the system, and the movements of the user's head and hands will be reflected in shape changes of the model's head and hands in another terminal, which is seen by another observer. In software development, we take a relatively simple path, that is, two terminals send each other user status data obtained by the HTC VIVE's positioning system. The HTC VIVE device was used here without full-body tracking devices, and thus the data captured only included the status of the user's head and hands. We assigned state data of the other user to the head and hand of the model in the scene, so as to complete morphological changes of the head and hand of the user identification (model) in the three-dimensional scene. Figure 4: Optical positioning schematic of HTC VIVE. In the concrete implementation, we added the component \"SteamVR_TrackedObject\" to the \"Controller (left)\" and \"Controller (left)\" of the object \"Camera\", in which all traceable devices were stored in this \"TrackedObject\" class.