**1. Introduction**

The development of computer games, the gaming industry in general, is "the driving force" in many ways behind the development of many technologies. From this point of view, perhaps the most important part of a computer game is its core. Its performance also determines the performance of the game itself. However, from the point of view of playability and game immersion, the interface of the computer game is also extremely important. Here is a very modern usage of just new technologies, one of which is virtual reality (VR) and its related technologies. Virtual reality interfaces represent a wide range of devices, applications, and ways to connect the user to the target game system. Recently, the current development of VR interfaces and systems has progressed in improving human–computer interaction (HCI).

In fact, there are three basic technological bases of systems that are used as a standard in accessing and interacting with users with three-dimensional environments or computer game objects. Each of these systems can work with a virtual context, but it differs in the way of displaying and controlling.

• Virtual reality (VR) is the first system with a fully immersive virtual environment. The basic definition says: "Virtual-reality system represents interactive computer system created an illusion of synthetic (virtual) space in real time based on

total simulation within the environment of close relation human – computing system." VR systems provide a better experience and they are more interactive, but the complexity of their implementation is greater. VR subsystems are mainly divided according to the senses that affect: Visualization subsystem, acoustic subsystem, kinetic and statokinetic subsystem, touch and contact subsystem, and other senses (e.g., a smell, a taste, and a sensitivity to pheromones). There is not much reason to implement some senses (which are commonly perceived in the real world) in the virtual world. For example, the taste is one such sensation at present. Through VR systems, the immersion of the user in computer games is controlled mainly at three standard levels: Visual, audio, and touch. Each of these levels provides a relevant way of feedback depending on the context of the virtual (gaming) environment.


As mentioned in Ref. [1], the existing VR, MR, and AR systems are beginning to merge under the area of innovative extended reality (XR), where "X" refers to the variable use of any of them (**Figure 1**). Thus, the current development of independent application platforms approaches the unification of these systems to the level of XR. The unification of VR, MR, and AR systems into the XR group creates a high presumption of improving user interaction and the level of immersion in a computer game.

According to Beglund [2], XR usage focuses mainly on interaction via wearable devices or sensory inputs. Huzaifa [3] highlights the potential of the XR interface in using hand gesturing inputs, which he considers necessary to achieve a fully natural interaction. XR extensions to support the web platform are also entering the realm of virtual collaboration. Today, the WebXR standard makes it possible to access XR devices via web browsers. This reinforces the creation of web systems with a wide

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

#### **Figure 1.** *XR system.*

range of interactions and inputs [4]. Seo [5] considers WebXR to be widely applicable mainly to support a wide range of interaction techniques. In this way, it is possible to extend the web application level for different purposes. According to Anthes [6], the use of web technologies for the VR application sphere is necessary, especially due to the current hardware and software diversity. This is also confirmed by Wang [7], who justifies the need to implement a web platform for the use of heterogeneous VR devices. The emergence of web VR applications has contributed to the expansion and globalization of collaborative virtual environments, including gaming environments. Paiva [8] attributes high potential to the deployment of web collaborative environments for the purposes of education and training, where it positively evaluates the benefits of sharing user/player interaction.

Using web platforms to share virtual environments and user interaction is possible, thanks to a high level of network infrastructure and technologies. In this way, systems are rapidly formed to support global virtual collaboration, where players can access a common virtual gaming space. The main advantage of the availability of such a system is the ability to connect players regardless of their actual geographical location in the world. Another advantage results from the refactoring of functions and modules of the web system. This refactoring is significantly faster and more efficient than in standard VR, MR, and AR applications. Despite these advantages, there are limitations to these systems that need to be solved.

The globalization of web systems increases the assumption of their use by a large group of users. This increases the probability that users will access the web system by using different types of devices and operating systems. In this case, there is a growing need to improve the adaptive features of the systems and their user interfaces so that they can provide the same control functions for different types of hardware and software platforms simultaneously according to the capabilities of individual players.

In collaborative virtual reality systems, multiuser interaction is shared in real time. This is necessary for many games. Given the context of a shared environment, there are ways to manage the interaction by which groups of players together access shared objects. As these systems continue to expand with different types of interactions

and functions, there is a growing need to improve the management of interaction techniques. Typical examples of extensions are physical and simulation subsystems or hardware components and control elements. The main problem occurs when multiple users/players use concurrent-subsystem-generated properties of shared objects or environments. In this case, a collision in the calculations may occur, and the shared interaction or virtual objects will be inconsistent. In the case of sharing the physical properties of objects, their chaotic behavior is often observable, while their consistency is different for each user at the same time.

Synchronization of shared interactions is highly efficient when a client–server network architecture is used. The sharing of interaction between players (clients) is controlled by a centralized computing node (server). The server provides information about the state of the virtual gaming environment for all clients in real time. The centralized compute node obtains data about each user's interactions. Then, it sends them to all members of the collaborative game group. The problem of sharing interactions is often associated with player-side resources/devices performance. These fully affect the rendering of the virtual environment, the processing of data from the server, and the control of the player's interaction. Insufficient computing performance of the user resources/devices is manifested by latency, which reduces the quality of collaboration. Therefore, it is necessary to focus on solving this problem area.

In the following subchapters of this chapter, the collaborative XR systems classifications are presented, followed by the concepts of the main application architectures and virtual game environment sharing consistency models. In conclusion, we briefly touch on object ownership sharing. The mentioned concepts and examples used in the chapter have been implemented in many works and projects (some examples are presented in the chapter too) using a collaborative environment (in a gamified form too) in the LIRKIS laboratory. The LIRKIS laboratory is a laboratory at the authors' home institution (Department of Computers and Informatics, Faculty of Electrical Engineering and Informatics, Technical University of Košice). The authors hope that readers will find here many tips and inspirations for their own work and they will also use practical notes on the advantages or disadvantages of individual systems.
