## 3 Results
### Scientific Mapping
#### 3.2.3 Hardware  
Virtual reality is a complex technology that integrates multimedia, sensors, displays, human-machine interactions, ergonomics, simulations, computer graphics, and artificial  
Figure 12: Ergonomics analysis that used the OWAS method [16]. intelligence technologies to expand human perception; therefore, virtual reality systems often require more than one device to function [13]. Virtual reality hardware can vary greatly depending on the application, ranging from a standard computer to certain display devices, motion capture equipment, and interactive gadgets, such as wearable devices, cameras, and head-mounted displays (HMD), etc. Table 4 shows the hardware, devices, and apparatus mentioned in the articles reviewed. We discovered a wide assortment of equipment, both in terms of the overall category and the models used in each category. Some studies did not mention which model was employed. We identified that the most frequently used equipment may be divided into five broad categories, as follows: (1) head-mounted displays, (2) CAVE Automatic Virtual Environment (CAVE), (3) motion capture systems, (4) optic tracking, and (5) projectors. Not only are these categories not mutually exclusive, but the overall structure is often created using a combination of multiple devices. A virtual reality environment requires the use of both visualization and tracking technology. In the industrial context, the most frequently used virtual reality visualization solutions are projection-based systems and head-mounted displays. Projection virtual reality systems include single or multiple projector-based powerwalls, as well as surrounding, walk-in setups, based on multiple projection screens (e.g., CAVEs). Head-mounted displays are devices attached to the virtual reality user's head, and typically include one or two displays as the image source, as well as collimating optics between the eyes and the display [5]. Ref. [13] noted that the use of CAVEs and head-mounted displays is rather rare in industry, which they attributed to expensive prices--a significant workload for manufactur \begin{table}
\begin{tabular}{c c c} \hline \hline
**Ref.** & **Hardware** & **Category** \\ \hline
[5,7,14,16,39,40,41,42,43] & HTC VIVE & \\
[13,37] & Oculus Rift & \\
[13] & Microsoft HoloLens & HMD \\
[13] & eMagin Z800 3 DVisor & \\
[13] & Sensics & \\
[13,30] & HMD (model unspecified) & \\ \hline
[5,13,30,35,43] & CAVE (model unspecified) & CAVE \\
[13] & CAVE aixCAVE & \\ \hline
[13,37,40,41] & Microsoft Kinect & \\
[6,13,38] & Vicon & Motion Capture \\
[1,6,13] & Motion Capture (model unspecified) & \\ \hline
[38] & Cameras & \\
[49] & optical tracking markerbased & \\
[13] & NDI POLARIS & optic tracking \\
[14,43] & Leap Motion & \\ \hline
[49] & Projector passive stereoscopic & \\
[6,35] & Projectors (model unspecified) & Projectors \\ \hline
[6,38] & 3D Printer & \\
[7,39] & Sensor Inertial Measurement Unit (IMU) (model unspecified) & \\
[6,13] & 3D glasses (model unspecified) & \\
[6,13] & Sound System AVR & \\
[49] & body markers, Camera InfraRed (model unspecified), single rear-projected wall & \\
[39] & full body suit, Heart Rate Monitor Polar V800 & Other devices \\
[37] & Hand Arm Vibration (HAV) & \\
[6] & Large screen for rear projection (model unspecified) & \\
[41] & Robot ABB IRB 2600 & \\
[13] & Augmented Reality devices, CyberGlove, Laser scanner VITUS XXL, SmartBody, & \\  & Smartphonephone, Volfoni Edge RF, Camera Firefly & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Hardware, equipment, devices, and apparatus used in the studies reviewed. ing process simulation, since the motions of digital human modeling are driven by actual people--and the time-consuming calibration process. We found a different scenario, since head-mounted displays were the most commonly utilized devices in the studies we examined. A plausible explanation is that, until recently, the usage of head-mounted displays was limited, owing to their expensive cost and technical limitations.