**2.1 Locally shared systems with centralized access**

Locally shared systems are related to the physical presence of players within a shared game space. Sharing the local environment by centralized players' access is equivalent to using a virtual cave system [9] (**Figure 2**). It contains a physically accessible environment with the possibility of players' group full immersion in real time. According to Nguyen [10], in a virtual cave system, the way of natural interaction between users is highly efficient and realistic, without the need to implement virtual avatars. Users cooperate in a jointly physically shared space. They are here realistically visible to each other [11]. According to Back [12], communication between users is in a natural way, without the need for external technology to share communication. In this case, any latency in users' communication with each other is excluded.

When using a locally available system with centralized user access, there are two basic types of interfaces (**Figure 2**), which are as follows:

• *User interfaces providing in-game player's interaction* with a shared virtual game environment [13]. They represent input subsystems for the control of the virtual

environment (e.g. touch interfaces, haptic controllers, sensor devices or gesticulation inputs).

• *Application interfaces*, the purpose of which is to obtain and process players' interactions and then submit them as feedback (visual, audio, and haptic). These interfaces provide program control between players' inputs and their subsequent processing into system outputs [14].

On the other hand, there are several limitations closely related, in particular, to the physical dimensions of such a system as well as to the multiuser interaction. In the case of virtual cave systems, the number of users collaborating/playing in real time is strictly limited. Another problem is the significant limitation of scene rendering for each user individually, mainly due to the use of stereoscopic visualization. The increasing number of users significantly multiplies the demands on the computing system performance due to the need to monitor their activity and movement simultaneously.

#### **2.2 Locally shared systems with separate access**

The local environment sharing using a separate user approach is the second way to collaborate within a common physical space. Different types of XR systems can be deployed with separate user access [15]. These systems can represent different data helmet technologies that communicate with each other via a communication node (**Figure 3**). The communication node creates a connection between separate systems, and it ensures the distribution of data. By default, the communication is controlled by using a local area network or another wireless standard. Nowadays, this type is quite popular in terms of games.

Each player is able to access the shared gaming virtual environment using their own separate system [16]. The most suitable for games is the deployment of XR systems using wireless technology, as it frees players from bonding to cable technology.

Unlike virtual cave systems, visual interaction is needed in this case [17], as users/players are not naturally visible to each other (unless MR systems are used). According to Horst et al. [18], users need to be replaced with virtual avatars. Then users/players in the virtual environment can communicate visually via these avatars. Furthermore, it is necessary to monitor the movement of users/players to avoid their physical collision during collaboration [19]. Today's XR technologies mostly include integrated free movement tracking subsystems that do not require the introduction of external technologies. The physical movement of the player is sensory processed by the integrated subsystem, and then, it is sent to the shared game virtual environment.

User's/player's interaction is created depending on the hardware technology used. Haptic and gestural input interfaces are most often used. The players are able to control and manipulate shared virtual objects with them.

Separate computing systems usage as, for example, data helmets give users/players much more freedom of movement and work with the broad context of the virtual game environment [20]. In this case, users/players move independently of each other, and they perform different types of activities simultaneously [21]. The group of collaborating users/players can be much larger than in virtual cave systems due to the use of separate computing systems.

*Collaborative XR Systems and Computer Games Development DOI: http://dx.doi.org/10.5772/intechopen.105555*

**Figure 3.** *Locally shared environment with separate user access (LIRKIS DCI FEEI TU Košice).*
