A 3 dimensional (3-D) user interface system employs: one or more 3-D projectors configured to display an image at a first location in 3-D space; one or more sensors configured to sense user interaction with the image and to provide user interaction information; and a processor configured (i) to receive the user interaction information from the one or more sensors; (ii) to correlate the user interaction with the image; and (iii) to provide one or more indications responsive to a correlation of the user interaction with the image, including displaying the image at a second location in 3-D space.