In my search for relevant interfaces for virtual worlds, I have found this description.
Researchers at the Massachusetts Institute of Technology have created a working prototype of a bidirectional LCD that allows a viewer to control on-screen objects without touching the screen.The bidirectional LCD screen, which captures and displays images, eliminates the need for any external controllers or touch contact. Hello,Minority Report.Ramesh Raskar, Matthew Hirsch and Henry Holtzman created the prototype at MIT’s Media Lab along with Douglas Lanman of Brown University.
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Same video on Vimeo.