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How Virtual Reality Works

In Summary

No matter what we call it, Virtual Reality is really about using computer technology to create a simulated, three-dimensional world that a user can manipulate and explore while feeling as if he were in that world.

 Jonathan Strickland

How Virtual Reality Works

What do you think of when you hear the words virtual reality (VR)? Do you imagine someone wearing a clunky helmet attached to a computerwith a thick cable? Do visions of crudely rendered pterodactyls haunt you? Do you think of Neo and Morpheus traipsing about the Matrix? Or do you wince at the term, wishing it would just go away?

If the last applies to you, you’re likely a computer scientist or engineer, many of whom now avoid the words virtual reality even while they work on technologies most of us associate with VR. Today, you’re more likely to hear someone use the words virtual environment (VE) to refer to what the public knows as virtual reality. We’ll use the terms interchangeably in this article.

Naming discrepancies aside, the concept remains the same – using computer technology to create a simulated, three-dimensional world that a user can manipulate and explore while feeling as if he were in that world. Scientists, theorists and engineers have designed dozens of devices and applications to achieve this goal. Opinions differ on what exactly constitutes a true VR experience, but in general it should include:

  • Three-dimensional images that appear to be life-sized from the perspective of the user
  • The ability to track a user’s motions, particula­rly his head and eye movements, and correspondingly adjust the images on the user’s display to reflect the change in perspective

In this article, we’ll look at the defining characteristics of VR, some of the technology used in VR systems, a few of its applications, some concerns about virtual reality and a brief history of the discipline. In the next section, we’ll look at how experts define virtual environments, starting with immersion.

Virtual Reality Immersion
How Virtual Reality Works
A virtual reality unit that allows the userto move freely in any direction
Photo courtesy of: VIRTUSPHERE

In a virtual reality environment, a user experiences immersion, or the feeling of being inside and a part of that world. He is also able to interact with his environment in meaningful ways. The combination of a sense of immersion and interactivity is called telepresence. Computer scientist Jonathan Steuer defined it as “the extent to which one feels present in the mediated environment, rather than in the immediate physical environment.” In other words, an effective VR experience causes you to become unaware of your real surroundings and focus on your existence inside the virtual environment.

Jonathan Steuer proposed two main components of immersion: depth of information and breadth of information. Depth of information refers to the amount and quality of data in the signals a user receives when interacting in a virtual environment. For the user, this could refer to a display’s resolution, the complexity of the environment’s graphics, the sophistication of the system’s audio output, et cetera. Steuer defines breadth of information as the “number of sensory dimensions simultaneously presented.” A virtual environment experience has a wide breadth of information if it stimulates all your senses. Most virtual environment experiences prioritize visual and audio components over other sensory-stimulating factors, but a growing number of scientists and engineers are looking into ways to incorporate a users’ sense of touch. Systems that give a user force feedback and touch interaction are called haptic systems.

The Virtual Reality
Other sensory output from the VE system should adjust in real time as a user explores the environment. If the environment incorporates 3-D sound, the user must be convinced that the sound’s orientation shifts in a natural way as he maneuvers through the environment. Sensory stimulation must be consistent if a user is to feel immersed within a VE. If the VE shows a perfectly still scene, you wouldn’t expect to feel gale-force winds. Likewise, if the VE puts you in the middle of a hurricane, you wouldn’t expect to feel a gentle breeze or detect the scent of roses.

Lag time between when a user acts and when the virtual environment reflects that action is called latency. Latency usually refers to the delay between the time a user turns his head or moves his eyes and the change in the point of view, though the term can also be used for a lag in other sensory outputs. Studies with flight simulators show that humans can detect a latency of more than 50 milliseconds. When a user detects latency, it causes him to become aware of being in an artificial environment and destroys the sense of immersion.

An immersive experience suffers if a user becomes aware of the real world around him. Truly immersive experiences make the user forget his real surroundings, effectively causing the computer to become a non entity. In order to reach the goal of true immersion, developers have to come up with input methods that are more natural for users. As long as a user is aware of the interaction device, he is not truly immersed.


NASA, the Department of Defense and the National Science Foundation funded much of the research and development for virtual reality projects. The CIAcontributed $80,000 in research money to Sutherland. Early applications mainly fell into the vehicle simulator category and were used in training exercises. Because the flight experiences in simulators were similar but not identical to real flights, the military, NASA, and airlines instituted policies that required pilots to have a significant lag time (at least one day) between a simulated flight and a real flight in case their real performance suffered.

For years, VR technology remained out of the publiceye. Almost all development focused on vehicle simulations until the 1980s. Then, in 1984, a computer scientist named Michael McGreevy began to experiment with VR technology as a way to advance humancomputer interface (HCI) designs. HCI still plays a big role in VR research, and moreover it lead to the media picking up on the idea of VR a few years later.

Jaron Lanier coined the term Virtual Reality in 1987. In the 1990s, the media latched on to the concept of virtual reality and ran with it. The resulting hype gave many people an unrealistic expectation of what virtual reality technologies could do. As the public realized that virtual reality was not yet as sophisticated as they had been lead to believe, interest waned. The term virtual reality began to fade away with the public’s expectations. Today, VE developers try not to exaggerate the capabilities or applications of VE systems, and they also tend to avoid the term virtual reality.

The bottom line? No matter what we call it, Virtual Reality is really about using computer technology to create a simulated, three-dimensional world that a user can manipulate and explore while feeling as if he were in that world.




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