...if you grab a brick in the real world, you feel the weight of the brick not only with your hand, but also throughout your entire arm and even in your back. Although restraining the hand or fingers is feasible, it would be tremendously difficult, if not outright impossible, to develop a system that simulates all the forces we encounter. What would the system look like? Perhaps the only way to create it would be to build a massive exoskeleton around a person that could move easily yet restrain movement when necessary.Even then, it would be difficult to simulate the feeling of a cat squirming in your hands or someone touching your cheek. And there's almost no way to effectively restrain or manipulate your body when it comes in contact with a virtual object. You'll never lean against walls in a virtual world or slip on a virtual banana peel. (Aukstakalnis and Blatner, 301)
Force feedback can give you a sense of the wall--but it can't support your weight in a lean.
At MIT, researchers are working on haptic problems; in the Research Laboratory of Electronics, testing subjects with anesthetized fingertips has made it possible to determine that "the perception of softness depends on the amount of force it takes to depress an object, its tactile quality against the skin, and information about how much the hand moves." (Cash, 9) In the Media Laboratory, a system called Sandpaper has been developed which imitates textures. Electric motors and brakes based on magnetic particles will activate a joystick that provides the sensation of writing on sandpaper with a pen.
And at the Artificial Intelligence Lab, development of software and devices to simulate contact with virtual objects has created a joystick that seems to touch visible but imaginary surfaces.
None of these researchers, however, expect VR users to be able to
experience the "illusion of touch" for ten years or more. "No one
yet knows enough about touch to fully simulate the feeling of
hitting a nail on the head."(Cash, 9)
Ivan Sutherland--The Ultimate Experience
In 1965, Ivan Sutherland, the father of Virtual Reality, noted in
an article that "the ultimate display would, of course, be a room
within which the computer can control the existence of matter."
(Sutherland, 506-508) Thus was born the holodeck.
Lawrence Krauss calls the holodeck "one of the most fascinating pieces of technology aboard the Enterprise." (Krauss, 99)
...the holodeck differs in one striking way from most of the virtual reality technologies currently under development. At present, through the use of devices that you strap on and that influence your vision and sensory input, virtual reality is designed to put the 'scene' inside you. The holodeck takes a more inventive tack: it puts you inside the scene. It does this in part by inventive use of holography and in part by replication. (ibid, 101)
Krauss, a physicist fascinated with twenty-third century technology, has made a careful study of the potentialities. He allows the possibility of complex and advanced holograms--but wonders at investing them with palpability. They have no corporeal integrity, which means that you can't touch them, much less dance, fight or have sex with them--or have one take your pulse. "Presumably, using transporter technology, matter is replicated and moved around on the holodeck to resemble exactly the beings in question, in careful coordination with computer programs that control the voices and movements of the re-created beings....When the transporter is turned off or the object is removed from the holodeck, the matter can then disassemble as easily as it would if the pattern buffer were turned off during the beaming process." (ibid, 107)
So here is how I envisage the holodeck: holograms would be effective around the walls, to give one the impression of being in a three-dimensional environment that extended to the horizon, and the transporter-based replicators would then create the moving 'solid' objects within the scene. Since holography is realistic, while (as I have explained earlier) transporters are not, one would have to find some other way of molding and moving matter around....one out of two technologies on hand isn't bad. (ibid, 108)
Krauss notes that "The holodeck represents what is so enticing about fantasy, particularly sexual fantasy: actions without consequences, pleasure without pain, and situations that can be repeated and refined at will." (Krauss, 100) He mentions this as part of a general discussion on "holodiction, and then notes that "Perhaps my concerns will appear as quaint in the twenty-third century as the warning cries accompanying the invention of television a half century ago." (ibid, 100)
I fancy Brenda Laurel's magic circle. If you catalog holodeck events in STSG, the majority of them are slanted that way; even the ones that go awry. But basically, I find myself in agreement with Aukstakalnis & Blatner:
...will it be possible to create realities so clear and complex that we won't be able to perceive the difference between our everyday reality and a computer-generated one? That's the Turing test of virtual reality, isn't it? If we can achieve that, we have created the ultimate computer environment.