What is Immersive Virtual Reality (VR)? As far as I'm concerned this type of VR involves all those cool toys like helmets and gloves used to bring the computer generated world closer to the user. The main components are a display right in front of the users eyes covering a wide field of view that adjusts to the users movements. The display is typically created by wearing a helmet. On the helmet there is a six-degree of freedom position tracker to sense the location and orientation of the users head. That position is constantly fed to the computer graphics display device which constantly recomputes the position and orientation of the scene as if the user was actually in it, or immersed.
VR has been around in various forms since the late 60s. The term Virtual Reality was coined by Jaron Lanier, one of the true visionaries of the computer world, and probably the only person with dreadlocks to testify before a U.S. congressional committee. Jaron's pioneering company that started the modern VR movement was called VPL and traces of its software still exist.
As far as I know the earliest example of an immersive VR system was created by Ivan Sutherland proposed in 1965 and demonstrated in 1968, a few short years after his seminal Sketchpad doctoral dissertation back in 1963. The immersive system created by Sutherland consisted of a large pole attached to a display device which was capable of displaying images right in front of your eyes. A primitive helmet. The pole (a sort of Sword of Damocles) was used to track the motion of the wearer so the display could be adjusted appropriately. Using this device you could walk around a room and turn your head all the while the image was updated appropriately. The idea was to give the user a sense of immersion.
Zap forward about 25 or so years and enter VPL which integrated a Head Mounted Display (HMD), a position tracker, and they invented the Data Glove. A glove that can sense the position of the fingers which can subsequently be used to control and interact with the virtual images being displayed in the helmet. There are several pages of hardware and software links on this site about HMDs position trackers, check em out!
VR went through type type of hype (even more so) that happened to VRML a few years back. It was the next big thing, on the cover of major magazines the salvation of the universe. Well not surprisingly it didn't live up to its hype, but technology is finally catching up to its promise. Helmets are getting better, position trackers are getting faster and compute power is rising dramatically.
One amazing example of just how far the technology has come can be seen from the Human Interface Technology (HIT) Lab part of the University of Washington. They now have a prototype display which is certainly the ultimate potential helmet. Called the Virtual Retinal Display (VRD) they are using a laser to paint the images directly on the retina of your eye! There are working prototypes and a serious effort to commercialize this thing. This device is the brainchild of Tom Furness (also the Director of the HIT Lab) whose been dreaming and/or working on this stuff for something nearly 25 years.
VR is being used to cure a variety of mental illnesses, and is a fabulous way of training surgeons. Combined with telerobotic devices VR technologies will enabling surgeons to treat people half way across the country or world.
One of the driving motivations for the creation of VRML and the other types of Web3D technologies has been the promise of immersive VR. VR represents the concrete realization of cyberspace elegantly created by William Gibson in Neuromancer (soon to be a movie). Strap on those glasses and hold on!
One Year Ago in Focus on Web3D (VRML) How Much VRML is Out There