You are certainly very familiar with standard input and output devices like the mouse, keyboard, screen and speaker. They are either logically one dimensional -- keyboard, speaker, teletype -- or logically two dimensional -- mouse, screen. Many less common devices, the trackball for example, are similarly logically two-dimensional. Thus, we should not be surprised if tasks that are inherently one-dimensional, like text processing, and tasks that are inherently two-dimensional, like illustration or page layout, are pretty well-served by existing input/output devices. We should also not be surprised if tasks that are inherently three-dimensional, like industrial design, are poorly served by existing devices.
A common sign that there are unsolved problems in a particular group of tasks is substantial effort at innovation in that general area, start-up companies, new products, academic research. By that measure the state-of-the-art in three-dimensional input devices leaves something to be desired. Typical applications that obviously benefit from such technology include complex visualization, industrial design and 3D computer animation. We see a variety of solutions to the three-dimensional input problem. Some are listed below, in roughly increasing exoticism. (There should be references for each, but life is short.)
In addition, methods have been evolved for some design activities that can be approached less interactively, specifying shape using geometric primitives, for example. Even so, much three dimensional computer-aided design is still performed in the following very kludgy way. A designer makes a shape using modelling clay; the shape is hand or laser scanned to get it into the computer; the computerized shape is painstakingly hand-editted; the result drives whatever computer-mediated processes follow: machining, mold-cutting, part layout, wire-routing, or whatever. The goal of this week's activity is to use modelling clay to do three-dimensional design, consider what unique properties it might have, and think about how they might be incorporated into a 3D input/output device.