# A Review on Methods and Systems for Remote Collaboration
## 4 Visual Display Technologies
### Virtual Reality (VR)  
Virtual reality is a visual technology that allows a person to immerse themselves completely in a digital world, independent of the physical environment, using special devices. The digital environment is computer-generated and contains objects and scenes that appear to be real. These environments can be used in training, games, or other live broadcast events. The user is equipped with a VR headset to access the applications that support VR. Popular VR devices include Oculus Rift [67], HTC Vive [68], and Oculus Quest [69].  
Traditionally, immersive technologies have been mostly used to facilitate guidance during the exploration of an unfamiliar environment. From 1970 to 1990, VR devices wereused for flight simulation, military training, and medical purposes. In the decade following 1990, these devices started to be commercialized for entertainment purposes. In recent years, VR devices have become more affordable. The combination of affordability and COVID-19 restrictions have fueled an enormous rise in their use [70].  
CoVar [71] is a mixed reality system that supports collaboration between augmented reality and virtual reality users by sharing a 3D reconstructed environment. The VR user wears an HTC Vive Lighthouse device, which displays a reconstructed mesh. The AR user captures his real, local environment and shares it with a remote augmented virtuality user. Both collaborate on the tasks in the shared space. The system enhances the communication by using awareness cues (field of view and gaze cues) and an AV-Snap-to-AR interface, which enables the AV user to control his head orientation. The interaction between the users is improved by eye-gaze, head-gaze, and hand gestures.  
[PERSON] et al. [72] presented a prototype for remote guidance that uses VR headsets for both the host and the remote user. The workspaces of the worker and the helper are captured using camera depth sensors, which results in sharing 3D environment data for the remote user, who can also track the worker's viewpoint. At the remote user's site, the sensors capture the helper's hands to indicate the instructions that have to be followed by the worker. Thus, in the shared virtual space, the worker sees the helper's hands overlaid on his own hands.  
The study in [73] focused on allowing the helper to have an independent view and study objects from any direction in a shared environment by capturing and reconstructing a copy of the local worker's space in 3D. Before the collaboration starts, the local user moves around their space using the VR device to capture all the details of the local environment. The remote helper can see the scene in a VR environment.  
[PERSON] et al. [74] proposed a remote collaboration in AR and VR intended to allow the remote expert to create or manipulate virtual replicas of the real objects. The remote user gives instructions to a local user by manipulating, pointing, or annotating the virtual objects in his VR environment. The same annotations appear in the AR environment of the local user. Both users wear a head-worn display (HWD).