Copyright is held by the author / owner(s).
SIGGRAPH Asia 2011, Hong Kong, China, December 12 – 15, 2011.
ISBN 978-1-4503-0807-6/11/0012
Ninja Track
Yuichiro Katsumoto
Keio-NUS CUTE Center
National University of Singapore
peropero@mixedrealitylab.org
Masa Inakage
Graduate School of Media Design
Keio University, Japan
inakage@kmd.keio.ac.jp
1 Introduction
Ninja Track is a belt shaped object which possesses the capacity to
alter its flexibility and hence strength. Using Ninja Track, we cre-
ated a game interface which can transform a whip into a sword and
also created a music instrument which produces sound depending
on its shape and interaction.
Figure 1: Ninja Track
2 Ninja Track
In the upcoming ubicomp era, various ideas have been proposed re-
garding user interfaces which can control analog materials. These
studies focus on computers altering the physical properties of ob-
ject such as shape, color, fur effects; as well as animating liquids
and paper. Based on these premises of phase transitioning objects,
we are investigating these ideas further to see how they transform
our future lifestyles. We call such objects as ’Phase Transition-ish
Apparatus(PTA)’.
The transformation of thermodynamic system is a representative
example of phase transition(e.g. water freezes at 0 degrees and boils
at 100 degrees). One aspect of such transformation is that of flexi-
bility, we present below a future vision where everyday objects and
interfaces are equipped with such characteristics.
Think of splints - if they were made of such PTA, they could be
folded into compact flexible fabric and carried easily by riders and
climbers. During casualties, the splints would regain their structure,
strength and rigidity by simply turning them into a strong stick.
The prototype Ninja Track which we made as an example of PTA,
provides the following functionalities:
The instant change in flexibility.
To become an interface to computers with the help of sensors
and actuators.
A ’multi-function device’ which changes its functions accord-
ing to the interactions.
Ninja Track consists at its modular level - a composition of two
parts - the vertical hinges and horizontal hinges. When flat, Ninja
Track is fluid and wavy. When the user folds it at the horizontal
hinges, Ninja track becomes a rigid stick. Both the parts are made
of ABS.
3 Applications of Ninja Track
Using Ninja Track, we created two applications. One is a phys-
ical game interface which can transform a whip into a sword
virtually and physically. This interface consists of Ninja Track,
MCU(Arduino Pro Mini), 3 axis accelerometer, servo motor, switch
and Max/MSP(MacBook Pro). In the normal state, the user can use
it as a whip when she/he swings it. When the switch is turned on,
Ninja Track is automatically folded by the servo motor and the user
can use it as a sword. Corresponding to the physical manipulations,
Ninja Track alters its form giving the user tangible feedback and a
more immersive experience.
Figure 2: Ninja Track Game Interface
Another application is a musical instrument which can make sounds
depending on its shape and interaction. It consist of Ninja Track,
MCU(xtel), 3 axis accelerometer, bend sensor, switches, and
Max/MSP(MacBook Pro). When Ninja Track is flat and the tact
switch is pushed, it makes sound of a recorder. When Ninja Track
is bent and the tact switch is pushed, it makes sound of a saxophone.
Further, when Ninja Track is a stick and the user shakes it, it makes
sound of a drum. When Ninja Track is made like a ring and shaken,
the sound of a bell is heard. And it makes a sound of harp when it
is rotated in a ring shape.
Figure 3: Ninja Track Music Instrument
Acknowledgement
This research is carried out under CUTE Project No. WBS R-705-
000-100-279 partially funded by a grant from the National Research
Foundation (NRF) administered by the Media Development Au-
thority (MDA) of Singapore.
