Tamotsu Murakami, Kazuhiko Hayashi,
Kazuhiro Oikawa, Naomasa Nakajima
Department of Engineering Synthesis, The University of Tokyo
Hongo 7-3-1, Bunkyo-ku, Tokyo 113, Japan
Tel.: +81-3-3812-2111 ex.6327
Fax: +81-3-3815-8356
E-mail: murakami@mech.t.u-tokyo.ac.jp
In present computer systems, standard input tools such as a mouse and a keyboard are normally used for 3-
D geometric shape manipulations as well as for 2-D ones. For highly 3-D shape deformations, e.g., twisting
the whole shape while bending it, however, these tools are not appropriate because they often require some
combination of indirect operations and do not provide users with direct and intuitive facilities. To solve the
problem, we propose the use of deformable objects as input tools (DO-IT) for direct and intuitive 3-D shape
deformation [1].
Figure 1 shows the basic concept of the DO-IT system.
FIGURE 1. Basic concept of DO-IT system
An objective shape to be manipulated is modeled and displayed on a computer screen, and a virtual control
volume to deform the shape is also defined. Then a deformable real object is prepared as an input tool
whose shape should be the same as, or at least close to, the control volume so that users can easily
understand the correspondence between them. The deformation of the tool can be electrically measured by
fabrication of a tool consisting of electrically conductive elastic material ,or attaching sensors, e.g., strain
gauges, on the surface and/or the inside of the tool. The measured deformation of the input tool is
processed and used to manipulate the objective shape in a computer. With this interface system, users can
deform the objective shape on a computer screen by performing direct and intuitive operations on the input
tool with bare hands aided by tactile feedback, such as pressing, bending, twisting, and combinations of
them.
This is a free-form deformation-oriented [2] approach. Even with an input tool of relatively simple shape,
such as a cube, practical shape manipulation can be achieved by adequately controlling the relative size,
position, and orientation of the control volume to the objective shape (Figure 2(a)(b)).
FIGURE 2. Deformation by control volume
Even though it may be somewhat difficult to stretch the input tool, such deformation as lifting the surface of
the shape can also be realized by pressing the other sides of the surface (Figure 2(c)). Since the input tool is
elastic, the deformation of the objective shape will be removed when users release the tool. By switching
an effect of input tool deformation on the objective shape on (the shape is editable) or off (the shape is
fixed), deformation of the shape can be maintained and accumulated (Figure 2(d)). In these shape
manipulations, a control volume is used as a 3-D shape editing cursor.
We have implemented a PC-based prototype of the DO-IT system with a cubical input tool. Figure 3 shows
the appearance and inside structure of the actual tool made of polyurethane foam (elastic and electrically
nonconductive; gray portion in the photograph).
Pieces of electrically conductive polyurethane foam (black portion in the photograph) are embedded on the
surface and the inside of the cube. These pieces are used as sensors to measure length by electrical
resistance. Resistances of all sensors are input into PC through an A/D converter. Based on the measured
sensor lengths (calculated from resistance) of the input tool, control volume deformation can be calculated,
which then determines the resulting objective shape deformation. Figure 4 shows the control volume and
the objective shape displayed on the prototype system screen.
FIGURE 4. Screen of DO-IT system
In this short note, we proposed a new concept of interface for direct and intuitive 3-D shape manipulations
using deformable objects as input tools, and the prototype system demonstrated the effectiveness and
promise of the concept. Some features of our basic concept have not been fully implemented in the PC-
based prototype yet, and we are currently working on a 3-D graphics workstation version with full features
and improved performance.
We would like to thank Mr. Toshihiro Yamamoto of INOAC Co. for technical advice on electrically
conductive polyurethane foam. This work has been supported by Nissan Science Foundation.
Abstract
Standard input tools such as the mouse and keyboard do not provide users with a direct and intuitive means
of 3-D shape manipulation. This study proposes a new concept of interface system for 3-D shape
deformation using a deformable real object as an input tool. By deforming the tool with bare hands with a
tactile feedback, users can manipulate a 3-D shape modeled and displayed on a computer screen directly
and intuitively. A PC-based prototype system with a cubical input tool made of electrically conductive
polyurethane foam demonstrates the effectiveness and promise of the concept.
Keywords:
Human interface, 3-D input tool, computer graphics, computer-aided design, free-form deformation
Introduction
BASIC CONCEPT
PROTOTYPE SYSTEM IMPLEMENTATION
CONCLUSIONS
ACKNOWLEDGEMENTS
