\chapter{Related Work}
\label{related}

In this chapter, some research on the integration of VR and human-computer interaction will be discussed. The relevant literature and its contributions will be briefly presented. The topic of VR and human-computer integration is an open research with many kinds of focus perspectives.

Robotic manipulation platforms combined with virtual worlds have several application scenarios. It can be used, for example, to train operators or to collaborate directly with real robots. Elias Matsas et al. \cite{Matsas:2017aa} provided a VR-based training system using hand recognition. Kinect cameras are used to capture the user's positions and motions, and virtual user models are constructed in the VR environment based on the collected data to operate robots as well as virtual objects, such as buttons. Users will learn how to operate the robot in a VR environment. The framework of VR purposed by Luis Pérez et al. \cite{Perez:2019ub} is applied to train operators to learn to control the robot. Since the environment does not need to change in real time, but rather needs to realistically recreate the factory scene, the VR scene here is not reconstructed in a way that it is captured and rendered in real time. Rather, a highly accurate 3D environment was reconstructed in advance using Blender after being captured with a 3D scanner.

Building 3D scenes in virtual worlds based on information collected by robots is also a research highlight. Wang et al. \cite{Wang:2017uy} were concerned with the visualization of the rescue robot and its surroundings in a virtual environment. The proposed human-robot interaction system uses incremental 3D-NDT map to render the robot's surroundings in real time. The user can view the robot's surroundings in a first-person view through the HTC-Vive and send control commands through the handle's arrow keys. The novel VR-based practical system provided by Patrick Stotko et al. \cite{Stotko:2019ud} uses distributed systems to reconstruct 3D scene. The data collected by the robot is fiest transmitted to the client responsible for reconstructing the scene. After the client has constructed the 3d scene, the set of actively reconstructed visible voxel blocks is sent to the server responsible for communication, which has a robot-based live telepresence and teleoperation system. This server will then broadcast the data back to the client used by the operator, thus enabling an immersive visualization of the robot within the scene.

Others are more concerned about the manipulation of the robotic arm mounted on the robot. Moniri et al. \cite{Moniri:2016ud} provided a VR-based operating model for the robotic arm. The user wearing a headset can see a simulated 3D scene at the robot's end and send pickup commands to the remote robot by clicking on the target object with the mouse. The system proposed by Ostanin et al. \cite{Ostanin:2020uo} is also worth mentioning. Although their proposed system for operating a robotic arm is based on mixed reality(MR), the article is highly relevant to this paper, considering the correlation of MR and VR and the proposed system detailing the combination of ROS and robotics. In their system, the ROS Kinect was used as middleware and was responsible for communicating with the robot and the Unity side. The user can control the movement of the robot arm by selecting predefined options in the menu. In addition, the orbit and target points of the robot arm can be set by clicking on a hologram with a series of control points.
