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Virtual reality interface
Interface of input device
Three dimensional position tracker: in virtual reality technology, the special hardware equipment used to measure the real-time change of the position and direction of three-dimensional objects is the tracker. In virtual reality applications, in order to control the observation direction and manipulate the objects, it is necessary to measure the movement of the user's head, hands and limbs. Another kind of information to be tracked is three-dimensional sound information. The performance parameters of the three bit tracker include: accuracy, jitter, deviation, and delay. The commonly used trackers are: mechanical trackers, electromagnetic trackers, AC electromagnetic trackers, DC electromagnetic trackers, ultrasonic trackers, optical trackers and hybrid inertial trackers.

(1) Roaming and manipulation interface this interface is a device that allows interactive changes in the virtual environment and the view in the exploration process by selecting and manipulating virtual objects of interest. Roaming and manipulation can be completed in absolute coordinate system or relative coordinate system. Another method to control the position of virtual reality technology object is through relative sensor, that is, the receiver is relatively static, and the absolute position data will never be 0. For relative position sensor, if no action occurs, it always returns 0. The commonly used roaming and manipulation interfaces include: roaming / manipulation interface based on tracker, tracking ball and three-dimensional probe.

(2) Gesture interface is a device to measure the real-time position of users' fingers. Its purpose is to realize the natural interaction based on gesture recognition in virtual environment. At present, most gesture interfaces are embedded with sensor gloves, which are used to measure the position of each finger relative to the head. The main differences between the various sensor gloves are: the type of sensor used, the number of sensors assigned to each finger, the sensing resolution, the sampling speed of the gloves, and whether they are wireless or range limited. Sensor gloves commonly used in the market include pinchglove, 5DT dataglove, didjigglove and cyberglove.

Interface of output device

As a kind of special hardware equipment, output devices provide users with feedback of simulation process on these inputs, and provide users with sensory channels for feedback through these interfaces, including vision (through graphic display device), hearing (through three-dimensional sound display device) and touch (through tactile display device).

(1) Graphic display device is a computer interface device, which displays the synthesized world image to one or more users interacting with the virtual world. When describing a graphic display device, the following features can be used: type of image generated, image resolution, field of view, display technology, ergonomic factors and price. Nowadays, graphic display devices are divided into: personal graphic display devices (helmet mounted display, handheld display, ground supported display devices, desktop supported realistic devices), large display devices (large display devices based on monitors, projector based displays).

(2) Sound display device is a kind of computer interface, which can provide synthetic sound feedback to users interacting with the virtual world. The sound can be mono or dual. The first three-dimensional sound generator was contracted by Crystal River Engineering for NASA in 1988. This fact data signal processor, called convol votron, consists of a set of PC compatible dual cards rotating in the housing. With the progress of digital signal processing (DSP) chips and microelectronics technology, today's convovotron is more compact. They are composed of a "convolution engine" that processes each sound source. Now the most commonly used is the three-dimensional sound based on speakers, and the simplest is stereo. In recent years, there have been relatively cheap PC three-dimensional sound cards. The DSP chip used processes the sound in stereo or 5.1 format, and outputs the real three-dimensional sound through convolution.

(3) Tactile feedback can be divided into two modes: contact feedback and force feedback. Contact feedback transmits real-time information such as the geometry of the contact surface, the surface hardness, temperature and so on. It will not actively resist the user's touch movement and can not prevent the user from passing through the virtual surface. Force feedback provides real-time information such as virtual object surface compliance, object weight and inertia. It can actively resist the user's touch movement and prevent the movement. The commonly used tactile feedback interfaces are: tactile mouse, cybertouch gloves, temperature feedback gloves, force feedback joystick, phantom arm, hapticmaster arm, CyberGrasp gloves, cy berforce, etc.

Virtual reality brain computer interface

Brain computer interface (BCI) is a new external information exchange and control technology that does not depend on the conventional brain information output pathway (peripheral nerve and muscle tissue) between the human brain and computers or other electronic devices. The first obvious use of BCI is to provide a new type of auxiliary motor function and means of external information exchange for people with normal thinking but incomplete motor function. Therefore, since the birth of BCI, the mainstream of its research and development is to control external devices and replace some missing functions of patients, or auxiliary text expression. Especially in recent years, BCI has made great progress in helping the disabled control prosthetics, wheelchairs, even spelling and typing, online games and so on. Recently, a novel BCI application mode has emerged in the field of multimedia and entertainment: combining BCI technology with virtual reality (VR) to form a new form of brain computer interface (bci-vr) based on virtual reality. The simplest way to realize the combination of BCI and VR is to design a BCI system that can provide users with immersive 3D virtual reality environment and on-site sensing feedback for real-time use. As soon as the new bci-vr technology appears, it shows unexpected scene effects and attractive application prospects at two levels.

On the one hand, as the input device of bci-vr system, BCI innovates the input mode of traditional VR system, which may completely change the way of interaction with virtual environments (VE); At the same time, BCI is more intuitive than the traditional VR system input mode, which can be regarded as similar to tactile sensing and VE for interaction and control. On the other hand, VR technology has become a very useful information feedback tool in BCI system. Compared with BCI's traditional simple feedback mode (the screen displays scalable 2D color bars to reflect brain thinking information output), VE can provide BCI users with a more proactive, colorful and stimulating situational feedback mode (closely related to brain thinking information output). Therefore, VR feedback can improve the learnability of BCI and shorten the training time, and VE can be used as the cheapest, most realistic, most reliable and safest training and testing scenario for BCI users before field use. The emergence of bci-vr new technology not only greatly benefits its traditional users - disabled patients, but also is particularly welcomed by a wide range of healthy public users. It is expected to become a new favorite of intelligent games and fashion entertainment.

In view of the fact that bci-vr new technology can take the advantages of both BCI and VR and complement each other, it has opened up the road of structural transformation and application innovation of these two technologies, showing attractive broad application prospects. This paper introduces the main research progress of bci-vr in recent years from the aspects of the basic composition of bci-vr system, the control transformation of BCI to VE and the feedback innovation of VR to BCI, and summarizes the existing difficulties and possible development trends in the future according to the author's experience, in order to communicate with readers and jointly promote the rapid development of bci-vr new technology.