The tentacles, spears, rocks, and other objects that jut out at you in 3-D IMAX theaters are first-rate illusions. But the spectacle is canned and grows less realistic if you move around the theater. You see exactly the same image regardless of where you sit. And you can't interact with the objects.
There are no such constraints in a new virtual-reality theater at Iowa State University. You can walk around a 3-D simulation of a tornado, for example, view it from all sides, and even step inside. In this 10x10x10-foot wireless environment, a computer generates the pictures, which are projected on all four walls, the floor, and the ceiling. The images on these panels serve as backdrops for 3-D objects that materialize in space.
Like IMAX theaters, this one creates 3-D objects by projecting separate images to the right and left lenses of the virtual reality goggles that each visitor wears. But here, the VR environment tracks you in real time by means of sensors on the goggles, which interact with the theater's pulsed magnetic field. The computer knows where you are looking, and tailors your view of the world.