Abstract By using a motion capture system we can measure and record human body
motion like ballet, dance or other performing arts. The data obtainedby the system are
very accurate, but the volume of the data is very large. E_cient handling and management
of the motion captured data are desired.
This paper describes a method of converting motion-captured data into dance notation
called Labanotation, which is well known among Western dance communities. Although the
description by Labanotation is not necessarily accurate, it is compact and powerful enough
to describe the overall body motion of dance and other intangible cultural properties. An
example of the result of processing is shown. 3D CG character animation has been produced
from converted Labanotation data. The Labanotation data produced from motion capture
data may also be used as an index for the archives of motion data.
1 Introduction
Today, motion capture systems have been used for measuring human body motion in the
_eld of CG-animation and movie production. The system can also be applied to recording
and archiving intangible cultural properties like dance and other performing arts. We can
obtain accurate 3-dimensional position data during body motion. However, it is still an
open issue how to generate a compact description of body motion like the one expressed as
\raising arms" etc .
The method of dance notation called Labanotation, which was devised by Rudolf Laban
in the early 20th century, has been used in recording body motions of ballet and dance[1].
Of course Labanotation is originally paper-based and was not intended to be computerized.
Moreover, the notation is not necessarily accurate. However, it is easy for us to roughly
grasp the body motion by browsing the score. A role of Labanotation for motion captured
data is just the same as the role of the music score for music performance. Multimedia
technology has already been introduced for preparing and editing Labanotation score[2, 3],
and it was proved useful for choreography and dance education.
This paper describes a method to generate data corresponding to Labanotation from those
obtained by motion capture systems.
2 Motion Capturing
Motion capture is a technique for measuring the motion of a multiply-linked rigid object
like human body. Several techniques have been devised, but we use an optical system, inwhich several markers are attached to the appropriate positions on the surface of subject
human body and the 3-dimensional positions of markers are algorithmically determined
from images captured by several, say 6 to 10, video cameras (Figure 1).
Figure 1: Motion capturing
The position of a marker does not necessarily represent the position of a joint of the
human body, which is essential for analyzing and reproducing human body motion. The
position of a joint is estimated by a software from the position of several markers around
it. We can get this kind of motion data which corresponds to the calculated joint position.
We use about 30 markers in measuring a motion, and we get 20 joint positions, which are
shown in Figure 2.
Figure 2: Joints of the body model
3 Labanotation and LND
3.1 Labanotation
Figure3 illustrates an example of a Labanotation score, which is extracted from a Labano-
tation textbook written by Hutchinson[1]. Labanotation score is drawn in a form of vertical
sta_ where each column represents the motion of a part of the body. Figure 4(a) shows the
basic arrangement of columns in the sta_. The motion of each body part is expressed by a
sequence of geometrical symbols placed in the corresponding column.
Figure 3: Example of Labanotation score[1]
Figure 4: Symbolism of Labanotation
Symbols for motion expression are classi_ed into several categories, but the most fun-
damental ones are the direction signs and the rotation signs. Direction signs describe the
translation of joints with achievement of a position in space by the joint, or with motion of
the joint in that direction. Rotation signs describe various forms of rotational motion.
Direction signs are expressed by polygonal symbols. Figure 4(b) shows the structure of the
symbol for direction signs. A single symbol for a direction sign represents three basic items
of information about a motion: Direction of horizontal motion is expressed by its shape,
vertical motion (levels) by its inside shading, and the duration by its size (i.e. length).
