Figure 3. (a) Lumen (photograph by Makoto Fujii, courtesy AXIS magazine); (b) The Source.

ally, but also haptically (through physical contact) or aurally, since moving objects may produce sound.

Therefore, the basic vocabulary of kinetic interface design includes speed, direction, and range of the motion of interface elements, which can be either rotational or linear positional movement. The forces that moving objects may apply to the user or other objects in the environment are another important design variable. Finally, the physical properties of interface elements, such as surface texture or surface shape can also be controlled and used for interaction. These define a very elementary vocabulary for interaction designers that can be used in creating kinetic interaction techniques.

Here, we discuss some of the approaches in designing kinetic interactions and illustrate the discussion with examples of several systems that have been developed. The overview is not intended to be an exhaustive survey of the current state in Kinetic Organic Interfaces, but rather categorize and indicate some of the directions of future development. As the field matures new concepts and applications will certainly appear.

Actuation in Dynamic Physical Controls. The first category of KOIs is the most straightforward application for actuation in user interfaces: dynamically reconfigurable physical controls. For example, PICO [ 8] and Actuated Workbench [ 7] use an array of electromagnets embedded in a table to physically move the input controls: pucks on a table top (see Figure 2a). The pucks can also be used as input devices. The important property of such interfaces is that they allow for maintaining consistency between the state of underlying digital data

b

and the physical state of interface controls. In one application the system is used for computing locations of cell phone towers; when the layout of towers was recomputed, the corresponding pucks physically move to reflect the new configuration.

Kinetic physical controls provide one possible solution for an important interface design challenge: how to create interfaces that are simple, yet provide sufficient functionality to control complex problems. In the kinetic approach used in PICO, controls can be provided “on demand,” simply adding them when needed, with the system repositioning elements according to the current state of the system. Another approach is to create physical controllers on the fly by modifying the shape of the control surface: this approach is investigated in shape-shifting kinetic displays that we discuss later.

Actuation as Embodiment of Information. As a communication medium, motion of elements in a KOI can be used to embody representations of data or changes in data. In static form, such an interface need not contain information, it is purely its kinetic behavior that communicates with the user. This approach has been investigated in ambient displays projects— displays communicating digital information at the periphery of human perception [ 4]. A classical example is the Pinwheels [ 1] project where a stream of data, such as stock market activity monitoring, is mapped to the motion of a set of pinwheels, speeding up clockwise if the markets are increasing, for example. Pinwheels exist purely as ordinary non-computational objects; it is only their motion, such as speed and direction, which allows them to become communication devices.

Another important use of kinetic motion for infor-