two dimensions, providing an additional feedback loop for computer output, and helping to resolve inconsistencies that otherwise arise from the computer’s inability to move objects on the table.

2.5-D deformable/transformable continuous tangibles (digital clay). A fundamental limitation of previous TUIs, such as Urp, was the lack of capability to change the forms of tangible representations during the interactions. Users had to use predefined, finite sets of fixed-form objects, changing only the spatial relationships among them, not the form of the individual objects themselves. Instead of using predefined, discrete objects with fixed forms, a new type of TUI system that utilizes continuous tangible materials, such as clay and sand, was developed for rapid form creation and sculpting for landscape design. Examples are Illuminating Clay [ 13] and SandScape. Later, this type of interface was applied to the browsing of 3-D volumetric data in the Phoxel-Space project.

Relief was created to explore direct and tangible interactions with an actuated 2.5-D shape display and to provide a kinetic memory of the forms and dynamic transformation capabilities. Recompose added midair gestures to direct touch to enable users to create forms (sculpt digital clay), and allowed us to explore a new form of interaction with 3-D tangible information using our bodies [ 14].

Antigravity tangibles. Actuated and transformable tangible interfaces have demonstrated a tangible world that is more dynamic and computer controllable, overcoming the limitations of atoms’ rigidity. The most fundamental constraint of tangibles comes from the gravity that governs our interaction with the physical world. The ZeroN

see
update material
to sync with the
digital model

touch or gesture

material transforms by itself

user gives form
or instructions
update
underlying
model

user constraints

constraints

factory constraints

• Figure 3. Interactions with radical atoms.

 

project [ 15] explores how removing the gravity from the physical world will alter our interaction with it (see sidebar on page 46). Although we focus on the transformable capability of materials in this article, we envision that the future of Radical Atoms would incorporate advanced capabilities, such as antigravity levitation or syncing forms among distributed copies (like in Touch [ 6]).

Concept of Radical Atoms

Radical Atoms is our vision for human interactions with dynamic physical materials that are computationally transformable and reconfigurable. Radical Atoms is based on a hypothetical, extremely malleable, and dynamic physical material that is bidirectionally coupled with an underlying digital model (bits) so that dynamic changes of the physical form can be reflected in the digital states in real time, and vice-versa.

To utilize dynamic affordance
as a medium for representation
while allowing bidirectional input
to control the shape and thus the
underlying computational model,
we envision that Radical Atoms
should fulfill the following three
requirements:
• Transform its shape to reflect
underlying computational state
and user input;

January + February 2012