What are the classifications of virtual reality systems?

4 types: 1. Immersive virtual reality system provides a completely immersive experience, making users feel as if they are in the real world. 2. Desktop virtual reality system uses personal computers and low-level workstations to generate interactive scenes in three-dimensional space. 3. The augmented virtual reality system allows users to observe the real world while superimposing virtual images on real physical objects. 4. Distributed virtual reality system, a system in which multiple users or virtual worlds located in different physical locations in the virtual world of the network are connected through the network to share information.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

With the rapid development and application of new technologies such as computer technology, network technology, and artificial intelligence, virtual reality technology has also developed rapidly and shown diversified development trends, and its connotation has also been greatly expanded. Virtual reality technology not only refers to those technologies that use a series of expensive equipment such as high-end visualization workstations and high-end helmet-mounted displays, but also includes all related technologies and methods with natural interaction and realistic experience.

Virtual reality technology The purpose is to achieve real experience and nature-based interaction, and it is impossible for ordinary units or individuals to afford the price of expensive hardware equipment and corresponding software. Therefore, we say that as long as the system can achieve some of the above purposes, it can be called a virtual reality system. .

In practical applications, we divide virtual reality technology into four typical types based on the degree of "immersion" and the degree of interaction: immersive virtual reality system, desktop virtual reality system, augmented reality system virtual reality system, distributed virtual reality system.

Among them, desktop virtual reality system is widely used in practical applications due to its very simple technology, strong practicability and low investment cost.

##1 , Immersive VR system

Immersive VR system (Immersive VR) is an advanced and ideal virtual reality system that provides a fully immersive experience that enables users to There is a feeling as if you are in the real world. It usually uses equipment such as cave-type stereoscopic display devices or helmet-mounted displays to first seal off the user's vision, hearing and other senses, and provide a new, virtual sensory space, using spatial position trackers, data gloves, and three-dimensional mice. and other input devices and visual, auditory and other devices, allowing users to have a feeling of being on the scene, fully involved and immersed in it.

The immersive virtual reality system has the following 5 characteristics:

1) High real-time performance

In an immersive virtual reality system, to achieve the same feeling as the real world, it must have high real-time performance. For example, when a person's head rotates to change the observation point, the spatial position tracking device must detect it in time, and the computer must perform calculations to change the corresponding scene of the output. It is required that there must be a small enough delay, and the change must be continuous and smooth.

2) High degree of immersion

The immersive virtual reality system uses a variety of input and output devices to create a virtual world and immerse the user in it, creating a "look like It is a multi-sensory three-dimensional virtual world that is real, sounds real, feels real, smells real, and tastes real. It also completely isolates users from the real world and is not affected by the real world outside. , can produce a high degree of immersion.

3) Good system integration and integration performance

In order to achieve all-round immersion for users, it is necessary for multiple devices to interact with multiple related software, and they cannot interact with each other. It has an impact, so the system must have good integration performance.

4) Good openness

The reason why virtual reality technology develops rapidly is that it adopts the results of other advanced technologies. In the immersive virtual reality system, the most advanced hardware equipment, software technology and software must be used as much as possible. This requires the virtual reality system to be able to easily improve the hardware equipment and software technology. Therefore, virtual reality must be constructed in a more flexible way than before. The software and hardware structure of the system.

5) Can support multiple input and output devices working in parallel at the same time

In order to achieve immersion, multiple devices may be required for comprehensive application. For example, if you hold an object with your hands, you must use a data glove. , space position trackers and other devices work synchronously. Therefore, parallel processing that supports multiple input/output devices at the same time is an essential technology for implementing virtual reality systems. Common immersive virtual reality systems include helmet-mounted display-based systems, projection virtual reality systems, and remote presence systems.

The helmet-based virtual reality system uses a helmet-mounted display to achieve a single-user stereoscopic visual output and stereophonic sound input environment, allowing the user to be fully immersed. It isolates the real world from it, allowing users to immerse themselves in the virtual environment from hearing to vision. The projection virtual reality system uses one or more large-screen projections to achieve the stereoscopic visual effects and stereoscopic sound effects of a large picture, allowing multiple users to feel fully immersed.

Remote presence system is a form of remote control, also known as remote control operating system. It consists of humans, human-machine interface, and remote-controlled robots. In fact, the remote-controlled robot replaces the computer. The environment here is the real environment where the robot works. This environment is far away from the user. It may be a working environment that humans cannot enter, such as a nuclear environment, a deep-sea working environment, etc. At this time, through virtual reality The system allows people to naturally feel this environment and complete the work in this environment.

2. Desktop virtual reality system

Desktop VR system (Desktop VR), also known as window virtual reality system, uses personal Devices such as computers or primary graphics workstations use the computer screen as a window for users to observe the virtual world, using technologies such as three-dimensional graphics and natural interaction to generate interactive scenes in three-dimensional space through various input devices including keyboards, mice, and torque balls. Manipulate the virtual world and interact with the virtual world.

Desktop virtual reality systems generally require participants to use a spatial position tracker and other input devices (such as data gloves and a three-dimensional space mouse with 6 degrees of freedom), so that although the user is sitting in front of the monitor, they can pass through The computer screen observes the virtual world within a 360° range. In a desktop virtual reality system, the computer screen is a window for users to observe the virtual world. With the help of some virtual reality tool software, participants can make various designs during the simulation process.

The hardware devices used are mainly stereoscopic glasses and some interactive devices (such as data gloves and spatial tracking devices, etc.). Stereoscopic glasses are used to view the stereoscopic effect of virtual three-dimensional scenes on a computer screen. The stereoscopic vision it brings can give users a certain degree of immersion. Sometimes in order to enhance the effect of the desktop virtual reality system, professional projection equipment can also be used in the desktop virtual reality system to increase the screen range and allow multiple people to watch.

Desktop virtual reality system mainly has the following three characteristics:

1) The user is in an incomplete immersion environment and lacks the feeling of complete immersion and immersion, even if he wears stereoscopic glasses , he will still be interfered by the real world around him;

2) The requirements for hardware equipment are extremely low, and some simple models even only require a computer, or add data gloves, spatial tracking settings, etc.;

3) Since the implementation cost of desktop virtual reality system is relatively low, its application is relatively common, and it also has some technical requirements of immersive virtual reality system.

Desktop virtual reality systems use less equipment and have low implementation costs. For developers and users, applying desktop virtual reality technology is the initial stage of virtual reality research.

3. Augmented virtual reality system (immersive virtual reality system)

Emphasizes human immersion in the immersive virtual reality system , that is, immersed in a virtual world, the virtual world in which a person lives is isolated from the real world, and the real world cannot be seen or heard. The augmented virtual reality system (Augmented VR) allows users to see both the real world and virtual objects superimposed on the real world. It is a system that combines the real environment and the virtual environment. It can reduce the cost of constructing a complex real environment (because part of the real environment is replaced by a virtual environment), and can operate on actual objects (because some objects are real environments), truly achieving a realm of both reality and fantasy. In augmented virtual reality systems, the information provided by virtual objects is often deep information that users cannot directly perceive with their own sensory organs. Users can use the information provided by virtual objects to enhance cognition in the real world.

The augmented virtual reality system mainly has the following three characteristics:

1) The integration of the real world and the virtual world;

2) It has real-time human-computer interaction function;

3) The real world and the virtual world are integrated in three-dimensional space.

The augmented virtual reality system can add virtual objects to the real environment. For example, in interior design, you can add decorative materials to doors and windows, change various styles, colors, etc. to review the final effect. achieve the purpose of augmented reality.

Common augmented virtual reality systems include: systems based on desktop graphics displays, systems based on monocular displays (one eye sees the virtual world on the display screen, and the other eye sees the real world), Systems based on optical see-through helmet-mounted displays and video see-through helmet-mounted displays.

Currently, augmented reality systems are commonly used in medical visualization, military aircraft navigation, equipment maintenance and repair, entertainment, restoration of cultural relics, etc. A typical example is when a doctor wears a see-through helmet-mounted display during virtual surgery. He can see not only the situation at the surgery site, but also various information needed during the surgery.

4. Distributed virtual reality system

In recent years, the simultaneous development and mutual promotion of computers and communication technologies have become the main features of the rapid development of information technology and industry around the world. In particular, the rapid rise of network technology has caused essential changes in the depth and breadth of information application systems. Distributed VR systems are a typical example. The distributed virtual reality system is the product of the development and combination of virtual reality technology and network technology. It is a system in the virtual world of the network where multiple users or multiple virtual worlds located in different physical locations are connected through the network to share information.

The goal of the distributed virtual reality system is to connect multiple users or multiple virtual worlds distributed in different geographical locations through the network based on the "immersive" virtual reality system, so that everyone can Several users participate in a virtual space at the same time, and the computer interacts with other users through the network to experience virtual experiences together to achieve the purpose of collaborative work. It elevates the application of virtual reality to a higher level.

There are two reasons why the virtual reality system runs under a distributed system: on the one hand, it makes full use of the powerful computing power provided by the distributed computer system; on the other hand, some applications themselves have distributed characteristics, such as multi-person Games and virtual war simulations are conducted over the Internet.

The distributed virtual reality system has the following characteristics:

• 1) Each user has a shared virtual workspace;

• 2) The behavior of pseudo-entities is realistic;

• 3) Supports real-time interaction and shared clock;

• 4) Multiple users can be different Communicate with each other;

• 5) Resource information sharing and allow users to naturally manipulate objects in the virtual world.

According to the number of shared application systems running in the distributed system, the distributed virtual reality system can be divided into two types: centralized structure and replication structure. The centralized structure refers to running a shared application system on a central server. This system can be a conference agent or a dialogue management process. The central server manages the input/output operations of multiple participants and allows multiple participants to share information. The advantage of the centralized structure is that it is simple in structure. At the same time, since the synchronization operation is only completed on the central server, it is relatively easy to implement. The disadvantage is: since input and output must be broadcast to all other workstations, there are higher requirements for network communication bandwidth, and all activities must be coordinated through the central server. When the number of participants is large, the central server often will become the bottleneck of the entire system.

In addition, because the entire system is very sensitive to network delays and highly dependent on the central server, the system robustness of this structure is not as robust as the replication structure. The replicated structure refers to replicating the central server on the machine where each participant is located, so that each participant process has a shared application system. The server receives input information from other workstations and transmits the information to the application system running on the local machine. The application system performs the required calculations and produces the necessary output.

The advantage of the replica structure is that it requires less network bandwidth. Since each participant only interacts with a local backup of the application system, the interactive response effect is good, and the output is generated on the local host, which simplifies the operation in the heterogeneous machine environment. The replicated application system is still single-threaded, and when necessary Multicast your status to other users.

The disadvantages are: it is more complex than a centralized structure, and it is more difficult to maintain information or state consistency among multiple backups in a shared application system. A control mechanism is required to ensure that each user gets the same input. The sequence of events to achieve a shared application system must be synchronized across all backups, and the output received by users should be consistent.

The most typical application at present is the SIMNET system. SIMNET is formed by connecting tank simulators through the network and is used for joint training of troops. Through SIMNET, simulators located in Germany and simulators located in the United States can run in the same virtual world and participate in the same combat exercises.

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