If you don't have a CAVE system or the cash to drop on a DataSuit, there are still a few options available to you to provide users a way of getting around a virtual environment without using a wand or joystick. Researchers believe devices that allow for more natural navigation within a VR environment also increase the user's sense of immersion. With this in mind, engineers and scientists developed a few different systems for user navigation.
One system is the treadmill. A treadmill is useful because the user remains stationary with respect to the real world, but feels as if he is actually walking through the virtual environment. Researchers have found it relatively simple to link a treadmill to a computer system so that a user's steps result in an appropriate adjustment in the system's graphics. An obvious limitation of normal treadmills is that you can only walk in two directions: backward or forward.
Some companies have developed omni-directional treadmills. These devices allow a user to step in any direction. Normal treadmills use a single motor, which exerts force either forward or backward relative to the user. Omni-directional treadmills use two motors -- from the user's perspective the treadmill can exert force forward, backward, left or right. With both motors working together, the treadmill can allow a user to walk in any direction he chooses on a walking surface wrapped around a complex system of belts and cables.
An alternative to a treadmill is a pressure mat. You may have seen pressure mats used with video games like "Dance Dance Revolution." There are many kinds of pressure sensors, though the most common are electromechanical pressure sensors. An electromechanical pressure sensor is a relay that activates when pressure is applied to the sensor. When the circuit closes, an electric current runs through it, signaling the CPU to make changes to the graphic output sent to the user.
The company VirtuSphere, Inc. offers a unique way for users to move around inside a virtual environment. It looks like a human-size hamster ball -- the user gets inside the sphere and walks around in it. The sphere rests on a stable platform that has several wheels resting against the sphere, allowing it to roll in any direction while staying in the same fixed position. Sensors in the wheels tell the CPU which way the user is walking, and the view within the user's HMD changes accordingly.
Within CAVE systems, some VR researchers are experimenting with a technique called passive haptics. "Haptics" refers to the sense of touch, so a haptic system is one that provides the user with physical feedback. A joystick with force-feedback technology is one example of a haptic interface device. Passive haptics are a little different in that they don't actively exert force against a user. Instead, passive haptics are objects that physically represent virtual elements in a VR environment. For instance, a real folding table might double as a virtual kitchen counter. Having something real to touch in a virtual environment enhances the user's sense of immersion and helps him navigate through the simulation.
In the next section, we'll look at the kinds of tracking systems you find in HMDs, DataGloves and other VR gear.