# Extended Reality: Types and Applications
## 6 Discussion  
This literature review analyzed modern technologies in the field of extended reality, including the following:  
* Application in various fields;
* Design features;
* Capabilities of popular XR devices;
* Software used in the development of applications and in the XR devices themselves;
* Possible improvements based on modern algorithms. The use of XR systems finds applications in various fields of activity. The classification of applications shown in Table 4 splits the identified studies into general categories without detail, and they are colored according the intensity of the research. The analysis of references took data from publicly accessible databases, including Scopus, Web of Science, Engineering Village 2, and Google Scholar. The items were sorted by relevant keywords. Rectified references were counted and presented under their section in Table 4. This approach cannot access the depth of research issues, such as the implementation mode, covered activities (Figures 9 and 10), and many others. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Usage** & **Virtual Reality** & **Augmented Reality** & **Mixed Reality** \\ \hline Education & 9440 & 4517 & 1077 \\ \hline Assistance & 77 & 96 & 160 \\ \hline Medicine & 1599 & 625 & 127 \\ \hline Architecture and design & 2837 & 1367 & 317 \\ \hline Manufacturing planning & 945 & 761 & 190 \\ and maintenance & 1865 & 1663 & 323 \\ \hline Navigation and tourism & 5297 & 1617 & 367 \\ \hline Entertainment & & & \\ and media & & & \\ \hline Military and rescue & & & \\ applications & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: XR classification based on facilities and opportunities. Figure 9: General applications in extended reality. However, such an approach provides the factor of research intensity, which shows an interest in this area within the scope of used technology. The uneven distribution of research between technologies leads to an understanding of each implementation field's convenience. For example, the use of headset devices limits the implementation of technology in media. However, in the assistance area, this limitation is absent. The low activity of VR, MR, and XR technologies in military and rescue areas signals the underdevelopment of applications and possible non-existent devices for field conditions with a long battery operation times, suitable shock-resistant devices, and devices suitable for autonomous operation without an Internet connection. Prevailing office-based implementation areas, such as education, planning, architecture, and entertainment, mostly rely on PC screen-based technologies, but XR headsets are still attractive for some entertainment and gaming applications. The discovered shortage of hardware shows a gap between possibilities and the real need for activity, especially in military and rescue. Classification of specialized applications here is provided in the Figure 10.  
Comparison of designs and capabilities used in popular VR, AR, and MR headsets showed that MR devices that use a screen for visualization and cameras to capture the view of the real world are the most versatile, since they can work in all three XR modes. The most optimal and popular was Meta Quest 3, due to its ability to work in three XR modes, good support for content creation programs, and a low price. In cases where it is important to always see the real world, a good and popular option would be Microsoft HoloLens, since its visualization system uses optics that allow you to see the real world with superimposed computer graphics. Having analyzed modern toolkits supporting XR (ARtoolkitX, Google ARCore, Apple ARKit, Vuforia, Unity XR, Unreal Engine XR, MRTK, MLSDK, OpenXR, and RViz), differences in functionality and compatibility with equipment and the possibility of applications in various tasks were revealed. As an example, Google ARCore and Apple ARKit are used to create mobile applications, and MRTK and OpenXR are used for cross-platform development.