Fig. 2 shows a typical Data Glove.
The Data-Glove is the device that most people think of when talking about VR input devices. It is the device that allows us to do everything in the virtual world that our real hand can do in the real world. The data glove is the translator from real to virtual. But there are too many degrees of freedom and too many possible device configurations, that the user simply has to come to the point where he fails to produce the correct position (gesture) to trigger the desired response by the system.
There should be a system which allows the user to know which gesture triggers which command (without the need of a trainer who gives the user a detailed description of the interface). Of course some gestures are very intuitive: grabbing an object, pointing in a direction, pointing at a object. But more abstract commands are hard to know by intuition alone. What gesture should the user apply to move into the direction he is pointing at?
This problem reduces the powerful data glove just to a pointing device where all other commands have to be performed by some abstract finger movements.
A very helpful device for the interation in the VR are haptics, force feedback devices. Such devices make it possible that the user feels virtual object that he touches or grabs.
But until today such devices not very practical, they are too big or too heavy to be used. They will trouble the user more then they help him.