## 5 Applications in Human-Robot Interaction
### Social Robotics  
The results of our review indicate that the use of game engines to build HRI applications using XR technologies for service and social robotics remains in its initial stages. In this context, a common application is to use a VR environment to replace a real robot, as presented in [70]. However, few works integrate real social robots with virtual environments \begin{table}
\begin{tabular}{p{14.2 pt}|p{142.3 pt}|p{142.3 pt}|p{142.3 pt}} \hline \hline
**Tool** & **Programming Languages** & **General Description and Main Capabilities/Functionalities** \\ \hline Vutforia Engine SDK & C++, Objective-C++, Java, and C\# & A framework for building Augmented Reality applications in Android, iOS, and Windows applications able to be executed on mobile devices and AR glasses. It provides free, academic, and premium plans. \\ \hline Google’s ARCore & Kottin/lava, Unity/C\#, Unreal/C++ & A framework for building Augmented Reality applications in Android, iOS, Unreal, and Unity. It uses motion tracking, environmental understanding, and light estimation to integrate virtual models with the real world \\ \hline Mixed Reality Toolkit & C\# & Is a cross-platform framework providing a set of components and features for accelerating Mixed and Augmented reality application development. Its functionalities include eye and hand tracking, spatial awareness, speech dictation, and XR device and game control manager. \\ \hline ZXing & Java & An open-source library for 1D/2D barcode image processing. Its functionalities include analysis and extraction of information from images containing barcodes or QR codes \\ \hline NuiTrack & C++, C\#, and Python & A 3D body tracking middleware. This framework can interpret depth maps as 3D point clouds, detect floor planes and background objects, detect and track persons, perform skeleton and hand tracking, and perform face analysis. \\ \hline OpenCV & C++/C, Python, and Java & A cross-platform and general-purpose real-time computer vision library. Its functionalities include image acquisition from RGB cameras, image segmentation and filtering, object recognition, camera calibration, and changing image color spaces, among many others. \\ \hline Find\_Object\_2D & C++ & A ROS-based package using a Qt interface that implements different feature detectors and descriptors for calculating the 3D position of objects using OpenCV \\ \hline MoveIt & C++ and Python & Robot motion planning framework enabling motion planning, manipulation, collision checking, 3D perception, kinematics, control, and navigation \\ \hline IAI Kinect & C++ & Collection of tools for enabling the use of Kinect with ROS using libreenet2 (a driver for Kinect) \\ \hline RobCog-IAI & C++ & Provides Unreal Engine plugins for building applications for robotics \\ \hline Newton VR & C\# & A VR interaction system enabling to pick up, throw, and use objects using tracked controllers \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._ \begin{table}
\begin{tabular}{p{142.3 pt}|p{142.3 pt}|p{142.3 pt}|p{142.3 pt}|p{142.3 pt}|p{142.3 pt}} \hline \hline \multicolumn{2}{p{142.3 pt}}{**Article**} & \multicolumn{2}{c}{**Hardware Integrated**} & \multicolumn{2}{c}{**Software Tools Integrated**} \\ \hline
**Year** & **Reference** & **XR Type** & **Robots** & **Devices** & **Communication** & **Interaction** \\ \hline
2019 & [68] & VR & Pepper & HTC VIVE & TCP/IP & NAO SDK \\ \hline
2021 & [60] & VR & QTRobot & Oculus Rift, phone phone & ROS and ROS bridge & NuiTrack, find Object\_2D \\ \hline
2022 & [69] & VR & NAO & Oculus Rift & ROS; ROS\# & NAO SDK \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Articles presenting XR solutions for social robotics. ments. An exception is [68], which uses a VR environment to investigate the differences between a real Pepper robot and its virtual representation by using both a virtual and a real robot simultaneously.