# Full-Body Motion Capture-Based Virtual Reality Multi-Remote Collaboration System
## 2 Literature Review
### Motion Capture  
Motion capture refers to a technology for extracting specific information using an algorithm using data concerning the movement, position, speed, and direction of objects, such as moving people and animals [52]. Motion capture is used not only in movies, but also in video games, sports, medicine, robotics, and defense. An early form of motion capture was the Rotoscoping technique devised by filmmaker [PERSON] in 1915. In this method, the movement of an actor was recorded with a camera and then moved and  
Figure 1: Avatar type (virtual reality environment). drawn one-by-one for each frame. Disney's first feature film, \"Snow White and the Seven Dwarves,\" was produced using the Rotoscoping method. This motion capture method provided a fluidity and realism not seen in previous animations [53]. Beginning in the 1970s, filmmakers designed new methods for capturing actors' movements using 3D optical technology. A computer was used to calculate the movements of an actor marked with a marker using a camera. Hollywood applied this approach to a 3D character named [PERSON] from Star Wars: The Phantom Menace in 1999. Since then, motion capture has developed as a camera performance method based on capturing motion data, and new motion capture methods have emerged [54]. Currently, motion capture technology is being used in many fields such as games, healthcare, and broadcasting. EA (Electronic Arts) used motion capture and artificial intelligence technology to capture the characteristics of a soccer player's actual movement to obtain data. By applying this hyper-motion technology to FIFA 22, realism and realism were increased [55]. Home-based virtual PT systems that use motion tracking sensors to monitor patient motions and provide guidance services are also of increasing interest [56; 57]. Motion capture makes it easy to capture the movement and expression of a subject. In the field of performing arts, motion capture technology is used to document, store, and learn the movements of dance, theater and martial arts [58]. Virtual influencers who perform virtual character activities using motion tracking equipment, face motion capture, and artificial intelligence technology are also spreading around the world [59]. As shown in Table 2, motion capture technologies can be classified into optical marker-based, marker-less, and inertial measurement methods [60]. The optical marker-based method marks a capture target with a marker to improve the measurement accuracy. This method requires dozens of cameras, as all markers on the subject must be always tracked. Although the accuracy of the body data is high, the process is time-consuming and expensive because it can only be shot in a fixed indoor studio. Optical marker-based imaging equipment companies include OptiTrack, Motion Analysis, and VICON. Microsoft Kinect is an optical markerless device. The Kinect V2 equipment can analyze a target using a camera sensor, infrared sensor, and depth sensor using 25 skeleton joint point algorithms [61]. Using this method, motion data can be obtained without attaching markers. However, the image processing method is inaccurate relative to those using markers or sensors because there is no clear reference point. Moreover, if the number of tracking personnel increases or the object is obscured, errors occur in the measurement values [62]. The inertial measurement method acquires motion data by attaching a sensor to the body joints of the user. Unlike marker-based methods, it is used for outdoor shooting or action scenes owing to its high portability and spatial freedom. However, when the sensor is used for a long time, the error range of the data widens. Companies related to inertial measurement equipment include Xsens, Noitom, NanSense, and Rokoko. Figure 2 shows the differences between the motion capture methods. Motion capture methods should be adopted and used with consideration of the characteristics and user environment of the platform to be manufactured.