Infitec). In order to improve the feeling of immersion, wearable multi-string cables offer haptics to complex geometries in virtual reality. These strings offer fine control of each finger joint to simulate the haptics involved in touching these virtual geometries. Special input devices are required for interaction with the virtual world. Some of the most common input devices are motion controllers and optical tracking sensors. In some cases, wired gloves are used. Controllers typically use optical tracking systems (primarily infrared cameras) for location and navigation, so that the user can move freely without wiring. Some input devices provide the user with force feedback to the hands or other parts of the body, so that the human being can orientate himself in the three-dimensional world through haptics and sensor technology as a further sensory sensation and carry out realistic simulations. This allows for the viewer to have a sense of direction in the artificial landscape. Additional haptic feedback can be obtained from omnidirectional treadmills (with which walking in virtual space is controlled by real walking movements) and vibration gloves and suits. Virtual reality cameras can be used to create VR photography using 360-degree panorama videos. 360-degree camera shots can be mixed with virtual elements to merge reality and fiction through special effects. VR cameras are available in various formats, with varying numbers of lenses installed in the camera. Visual immersion experience Display resolution Minimal Angle of Resolution (MAR) refers to the minimum distance between two display pixels. At the distance, viewer can clearly distinguish the independent pixels. Often measured in arc-seconds, MAR between two pixels has to do with the viewing distance. For the general public, resolution is about 30-65 arc-seconds, which is referred to as the spatial resolution when combined with distance. Given the viewing distance of 1m and 2m respectively, regular viewers won't be able to perceive two pixels as separate if they are less than 0.29mm apart at 1m and less than 0.58mm apart at 2m. Image latency and display refresh frequency Most small-size displays have a refresh rate of 60 Hz, which adds about 15ms of additional latency. The number is reduced to less than 7ms if the refresh rate is increased to 120 Hz or even 240 Hz and more. Participants generally feel that the experience is more immersive with higher refresh rates as a result. However, higher refresh rates require a more powerful graphics processing unit.