What do you think of when you hear the words virtualreality (VR)? Do you imagine someone wearing a clunky helmet attached to a computer with 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
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.
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.
For immersion to be effective, a user must be able to explore what appears to be a life-sized virtual environment and be able to change perspectives seamlessly. If the virtual environment consists of a single pedestal in the middle of a room, a user should be able to view the pedestal from any angle and the point of view should shift according to where the user is looking. Dr. Frederick Brooks, a pioneer in VR technology and theory, says that displays must project a frame rate of at least 20 - 30 frames per second in order to create a convincing user experience.
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. In the next section, we’ll look at the other facet of telepresence: interactivity.
Passive haptics are one way VE developers have tried to enhance
interactivity. Passive haptics are real objects in a physical space that
are mapped to virtual objects in a virtual space. Users wear an HMD or
similar portable display while in the physical space. When they look
toward the physical object, they'll see the virtual representation of it
in their display. When they approach the object and try to touch it,
they encounter the real object in the physical space. Anything a user
does with that object in real space appears as a reflected action upon
the virtual object in virtual space.
Swimming in VR systems doesn’t refer to jumping into a pool -- it describes the effect of latency within a virtual environment. If you were to look around in a VE and notice that the change in point of view was not instantaneous, you would experience swimming. The effect is distracting and can even make you experience motion sickness, called simsickness or cybersickness in VR circles.