Today, most VE systems are powered by normal personal computers. PCs are sophisticated enough to develop and run the software necessary to create virtual environments. Graphics are usually handled by powerful graphics cards originally designed with the video gaming community in mind. The same video card that lets you play World of Warcraft is probably powering the graphics for an advanced virtual environment.
VE systems need a way to display images to a user. Many systems use HMDs, which are headsets that contain two monitors, one for each eye. The images create a stereoscopic effect, giving the illusion of depth. Early HMDs used cathode ray tube (CRT) monitors, which were bulky but provided good resolution and quality, or liquid crystal display (LCD) monitors, which were much cheaper but were unable to compete with the quality of CRT displays. Today, LCD displays are much more advanced, with improved resolution and color saturation, and have become more common than CRT monitors.
Other VE systems project images on the walls, floor and ceiling of a room and are called Cave Automatic Virtual Environments (CAVE). The University of Illinois-Chicago designed the first CAVE display, using a rear projection technique to display images on the walls, floor and ceiling of a small room. Users can move around in a CAVE display, wearing special glasses to complete the illusion of moving through a virtual environment. CAVE displays give users a much wider field of view, which helps in immersion. They also allow a group of people to share the experience at the same time (though the display would track only one user’s point of view, meaning others in the room would be passive observers). CAVE displays are very expensive and require more space than other systems.
Closely related to display technology are tracking systems. Tracking systems analyze the orientation of a user’s point of view so that the computer system sends the right images to the visual display. Most systems require a user to be tethered with cables to a processing unit, limiting the range of motions available to him. Tracker technology developments tend to lag behind other VR technologies because the market for such technology is mainly VR-focused. Without the demands of other disciplines or applications, there isn’t as much interest in developing new ways to track user movements and point of view.
Input devices are also important in VR systems. Currently, input devices range from controllers with two or three buttons to electronic gloves and voice recognition software. There is no standard control system across the discipline. VR scientists and engineers are continuously exploring ways to make user input as natural as possible to increase the sense of telepresence. Some of the more common forms of input devices are:
- Force balls/tracking balls
- Controller wands
- Voice recognition
- Motion trackers/bodysuits