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 computer with a thick cable? 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.

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.

Virtual Reality 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. An effective VR experience causes you to become unaware of your real surroundings and focus on your existence inside the virtual environment.

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. 

The Virtual Reality Environment

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.

Virtual Reality Interactivity

Immersion within a virtual environment is one thing, but for a user to feel truly involved there must also be an element of interaction. Early applications using the technology common in VE systems today allowed the user to have a relatively passive experience. Users could watch a pre-recorded film while wearing a head-mounted display (HMD). They would sit in a motion chair and watch the film as the system subjected them to various stimuli, such as blowing air on them to simulate wind. While users felt a sense of immersion, interactivity was limited to shifting their point of view by looking around. Their path was pre-determined and unalterable.

Today, you can find virtual roller coasters that use the same sort of technology. DisneyQuest in Orlando, Florida features CyberSpace Mountain, where patrons can design their own roller coaster, then enter a simulator to ride their virtual creation. The system is very immersive, but apart from the initial design phase there isn't any interaction, so it's not an example of a true virtual environment.

Interactivity depends on many factors. Steuer suggests that three of these factors are speed, range and mapping. Steuer defines speed as the rate that a user's actions are incorporated into the computer model and reflected in a way the user can perceive. Range refers to how many possible outcomes could result from any particular user action. Mapping is the system's ability to produce natural results in response to a user's actions.

Navigation within a virtual environment is one kind of interactivity. If a user can direct his own movement within the environment, it can be called an interactive experience. Most virtual environments include other forms of interaction, since users can easily become bored after just a few minutes of exploration. Computer Scientist Mary Whitton points out that poorly designed interaction can drastically reduce the sense of immersion, while finding ways to engage users can increase it. When a virtual environment is interesting and engaging, users are more willing to suspend disbelief and become immersed.

True interactivity also includes being able to modify the environment. A good virtual environment will respond to the user's actions in a way that makes sense, even if it only makes sense within the realm of the virtual environment. If a virtual environment changes in outlandish and unpredictable ways, it risks disrupting the user's sense of telepresence.