When you think about virtual reality, you generally image a geek in a wraparound headset (HMD) and datagloves connected to a powerful workstation or supercomputer. The nature of the input and output distinguishes VR from a typical computer experience (such as writing an essay or playing games on your computer). In contrast to traditional computers, which employ input devices such as a keyboard, mouse, or (more exotically) speech recognition, VR uses sensors to detect how your body moves. VR employs two screens (one for each eye), stereo or surround-sound speakers, and maybe various types of haptic (touch and body perception) feedback, where a PC displays output on a screen (or a printer). Let’s look at some of the most prevalent virtual reality input and output devices.

Displays that are worn on the head (HMDs)

From the inside, here’s what it looks like. A common HMD contains two small displays that show different visuals to each of your eyes, resulting in a composite 3D (stereoscopic) vision produced by your brain. The photo is courtesy of the United States Air Force.

There are two significant distinctions between VR and traditional computer viewing: with VR, you see a 3D image that changes fluidly and in real-time as you move your head. Wearing a head-mounted display, which resembles a huge motorcycle helmet or welding visor but is made up of two tiny shows (one in front of each eye), a blackout blindfold that shuts out all other light (removing distractions from the actual world), and stereo headphones, makes this feasible. The two screens provide slightly different stereoscopic pictures, giving the virtual world a convincing 3D viewpoint. HMDs often have built-in accelerometers or position sensors, which allow them to detect how your head and torso move (both position and orientation—which direction they’re tilting or pointing) and adapt the image appropriately. The problem with HMDs is that they’re rather heavy, making them difficult to wear for long periods; some of the truly hefty ones are even installed on counterweighted supports. But HMDs don’t have to be that complicated: Google has created a low-cost set of cardboard goggles with built-in lenses that turn an average smartphone into a primitive HMD.

Rooms that immerse you

Sitting or standing within a room with changing graphics projected from outside is an alternative to wearing an HMD. As you go about the room, the visuals change. Images of landscapes, cities, and airport approaches are frequently projected onto big displays immediately outside a facsimile of a cockpit in flight simulators. CAVE (Cave Automatic Virtual Environment), a well-known VR experiment established at the University of Illinois by Thomas de Fanti in the 1990s, works similarly. People moved around within a big cube-shaped chamber with semi-transparent walls onto which stereo pictures projected from outside were displayed. They didn’t need to use HMDs, but they did require stereo glasses to get a complete sense of 3D.


When you see something great, it’s natural to reach out and touch it—even newborns do it. As a result, allowing users to interact with virtual items has always been a key aspect of VR. Datagloves, which are conventional gloves with sensors linked to the outside to monitor hand and figure motions, are commonly used for this. Fiber-optic cables extending each finger’s length are one technological means of accomplishing this. Each wire has microscopic slits in it, allowing more or less light to escape when you flex your fingers back and forth. A photocell at the cable’s end measures the amount of light that reaches it, and the computer utilizes this information to figure out what your fingers are doing. Other gloves employ strain gauges, piezoelectric sensors, or electromechanical devices (such as potentiometers) to monitor finger movements.


A wand is a stick that you may use to touch, point at, or otherwise interact with a virtual environment. It’s even easier than a dataglove, and it has built-in location and motion sensors (such as accelerometers), mouse-like buttons, and scroll wheels. Initially, wands were crudely hooked into the main VR computer; now, they are becoming increasingly wireless.

Virtual reality applications

Virtual reality has long been thought to be nothing more than a glorified arcade game—a “dreamy escape” from reality. In this respect, the phrase “virtual reality” is a misnomer; proper names would be “alternative reality,” “manufactured reality,” or “computer simulation.” The most important thing to remember about virtual reality is that it isn’t a fad or fantasy that will whisk people away to alternate worlds; it is a hard-edged practical technology that has been routinely used by scientists, doctors, dentists, engineers, architects, archaeologists, and the military for nearly 30 years. What will we be able to accomplish with it?


Training for difficult and risky vocations is difficult. How can you prepare for a journey to space, a jumbo aircraft landing, a parachute jump, or brain surgery in a safe manner? All of them are excellent prospects for virtual reality applications. As we’ve seen, Flight cockpit simulators were among the first VR applications; they can be traced back to mechanical simulators constructed by Edwin Link in the 1920s. Surgeons, like pilots, are now frequently taught using virtual reality. In a 2008 survey of 735 surgical trainees from 28 nations, 68 percent thought the option to train with virtual reality was “good” or “great,” while only 2% stated it was “useless” or “unsuitable.”