RE: Motion capture as subset of Motion Tracking

From: Richard Widgery (motion@widgery.demon.co.uk)
Date: 01/07/02


Lisa,

I do agree with your "triggering" comments but not that motion capture is a
subset of motion tracking (at least not in the way you described).

I agree that the term "motion tracking" is a larger descriptor than
"capture" in narrow field of animation, but not generically since to track
you first must capture, then analyse.  Video, magnetic, encoder,
potentiometer, ultra-sonics are all capture technologies, and would turn
your comment the other way around to say - "Video based motion tracking uses
video motion capture technology, & magnetic motion tracking uses magnetic
capture technology". However I would not say that motion tracking is a
subset of motion capture.

I would also like to address the intention of the manufacturers of these
systems.  I have read a number of mails on this news listing equate "motion
capture" with the 3D animation industry even when Oxford Metric's "Vicon"
and Motion Analysis' "Falcon" systems originated and still have MUCH larger
market strongholds in medical research and biomechanics.  At Jim Henson's
Creature Shop - UK I was fortunate enough to be the one of the first in the
world to use and develop Vicon systems for the 3D Animation industry in
1993, a time when we used only 5 cameras and pretty lengthily video->data
reconstruction software.  We collaborated with Oxford Metrics on Beta
testing and some design features to improve the pipe-line for the animation
industry since the only other systems being used were in medicine and
research outfits that had different working practices and requirements.  I
suppose Animation is the publicised end of the spectrum but by no means the
norm or largest user-base.

Generally I would not use the term tracking since that almost implies that
the end result is a direct consequence of the movement of the subject -
which it is not necessarily true.

Regards,

Richard Widgery
richardw@kinetic-impulse.com


KINETIC IMPULSE - Digital Performance Art & Science
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87 Hadlow Road, Tonbridge, Kent, TN9 1QD, England
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-----Original Message-----
From: owner-dance-tech@lists.acs.ohio-state.edu
[mailto:owner-dance-tech@lists.acs.ohio-state.edu]On Behalf Of Lisa
Naugle
Sent: 06 January 2002 04:42
To: dance-tech@lists.acs.ohio-state.edu
Subject: Motion capture as subset of Motion Tracking


>How about calling the motion capture for animation "motion capture" and
>referring to the second form as "motion trigger."  The second form of
>technology is more about triggering a pre-scripted event, whether that be a
>sound, light, or video projection, while the first is about "capturing" or
>documenting precise movements made by the entire body through time.

The term "Motion Tracking" is often used to describe video based motion
"sensing" and in an environment where there is mutual influence
(interactivity) between movement and other media.    The object (presence
of the dancer) is "tracked" in space and time and influences the events.
The word "triggering" implies a control paradigm which is more limiting and
in my experience, less useful than a paradigm of tracking or mutual
influence.   Trigger means "this" causes "that" and is a one-to-one mapping
between a movement and an event.  Triggering implies a single thing is
happening...turing on and off...a  binary condition.  Whereas mutual
influence implies  more room for nuance and other forms of interactivty
rather than straight forward trigggering.  Motion tracking can be used for
interactivity, that is tracking the attributes of the motion in the video.

Motion capture  is a sub-set of motion tracking, that is, tracking markers
of a moving object or person.  It is a very specific method.   Motion
capture is a form of motion tracking that is speciialized for the needs of
3D animation.

Video based motion capture uses video motion tracking technology to make
itslef happen.    Magnetic motion capture uses magnetic motion tracking
technology.

Best,
Lisa
=====================================
Dr. Lisa Naugle
Assistant Professor
Dance and Technology
University of California, Irvine
School of the Arts, Department of Dance
MAB 300
Irvine, California  92697-2775
email:  lnaugle@uci.edu
tel:  (949) 824-3209
fax:  (949) 824-4563
http://www.arts.uci.edu/lnaugle/



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