The inherent need of humans to communicate acted as the moving force for the formation, expansion and wide adoption of the Internet. The need for communication and collaboration from distance resulted in the evolution of the primitive services originally offered (i.e., e-mail) to advanced applications, which offer a high sense of realism to the user, forming a reality, the so-called virtual reality. Even though virtual environments were first introduced as stand alone applications, which could run on a single computer, the promising functionalities of this new form of representation and interaction as well as the familiarity of the users with it drew increased research interest. This fact resulted in virtual reality to be viewed as the solution for achieving communication and collaboration between scattered users, in various areas of interest, such as entertainment, learning, training, etc. This led to the creation of Networked Virtual Environments (NVEs). In particular, NVEs were first introduced in the 1980’s and the first areas that exploited the newborn technology were military and entertainment applications. In particular, the U.S Department of Defense played an important role to the direction of applications, protocols and architectures for this promising technology. In the 1990’s, where academic networks became a reality, NVEs drew increased academic research interest and a variety of applications and platforms were developed. In particular, the academic community has reinvented, extended, and documented what the Department of Defense has done. The evolution and the results extracted by research on this field were widely adopted from multiple areas of interest, with main representative the entertainment area. Since 2000, where virtual reality technology, processing power of computers and the network were significantly improved, a wide variety of systems, protocols and applications were developed. In particular, the familiarization the end users with the Internet and the promising advantages and opportunities of Virtual Reality contributed to currently view NVEs as an effective tool for supporting communication and collaboration of scattered users. Currently, the application areas of NVEs have been widely expanded and their use can be found at military and industrial team training, collaborative design and engineering, multiplayer games (Zyda, 2005), mobile entertainment, virtual shopping malls, online tradeshows and conferences, remote customer support, distance learning and training, science, arts, industry, etc. Summarizing, NVEs nowadays tend to consist a powerful tool for communication and collaboration, with applications ranging from entertainment and teleshopping to engineering and medicine. To this direction, in the recent years important active research on this topic in both academic and industrial research is taking place.
NVE is a twofold term. Even though the “Virtual Environments” part prevails, the “networked” substance changes the meaning and nature of these environments. Regarding the Virtual Environment, it can be considered as a simulation generated by a computer, which can simulate either an imaginary or real world. Even though Virtual Environments can be two-dimensional, the term is mainly related to three-dimensional environments that aim at providing to the users a high sense of realism by incorporating realistic 3D graphics and stereo sound, to create an immersive experience. As far as it concerns the “networked” part of the term, this dimension is mainly related to the support of multiple concurrent users, scattered around the globe, even though NVEs can be single user applications. A definition provided by Singhal and Zyda (1999) states that “NVEs are software systems that can support multiple users, which can interact both with each other and with the environment in real time and aim at providing to the users a high-sense of realism by incorporating 3D graphics and multimedia.”
The concept of a NVE is simple. Two or more users can view the Virtual Environment (VE) on their computer, having their own local copy of the virtual world. For achieving high-sense of realism and maintaining consistency, when a user performs actions on one computer, these actions are propagated through the network to other participating computers for keeping all copies of the VE synchronized. The participants constitute active parts of the VE, usually represented by human-like entities, called avatars for enhancing the awareness (Joslin, Pandzic & Thalmann, 2003).
Key Terms in this Chapter
HLA: High Level Architecture is a general purpose architecture for distributed computer simulation systems. Using HLA, computer simulations can communicate to other computer simulations regardless of the computing platforms.
NVE: Networked Virtual Environment is a virtual environment that allows a group of geographically separated users to interact in real time
DVE: Distributed Virtual Environment is an NVE where active parts of the virtual environment are scattered to different computers, which are connected through the network.
VRML: Virtual Reality Modeling Language is a standard file format for representing 3D interactive vector graphics, designed particularly with the World Wide Web in mind.
Java 3D API: The Java 3D API is a hierarchy of Java classes which serve as the interface to a sophisticated three-dimensional graphics and sound rendering system. Java 3D provides high-level constructs to create and manipulate 3D geometry, and to build the structures used to render that geometry.
VE: Virtual Environment is a computer-generated simulation with which the user can interact in such a way that he receives real time feedback aiming to provide its users with a sense of realism.
X3D: Extensible 3D is the open standard for Web-delivered 3D graphics. It specifies a declarative geometry definition language, a run-time engine, and an application programming interface that provide an interactive, animated, real-time environment for 3D graphics.
DIS: Distributed Interactive Simulation is an open standard for conducting real-time platform-level wargaming across multiple host computers and is used worldwide especially by military organizations but also by other agencies such as those involved in space exploration and medicine.