CS 6353
Computer Graphics and
Multimedia
Motion Capture
By
Vanitha Kowdeed
Overview:
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Definition of Motion Capture
History of Mocap
Rotoscoping
Types of Motion Capture
Prosthetic
Optical
Electromagnetic
Acoustic
Marker Placement
Production Pipeline
Objects for Mocap
Skin Deformation
Examples
References
What is Motion Capture?
A process by which a movement can be recorded
digitally.
Or
Motion Capture of an object involves sensing,
digitizing, and recording that object in motion
– Whole body
– Hands
– Face
• One way of acting out an animation
Originally used for military tracking purposes.
 In sports, motion capture acts as a tool for
biomechanic research that is focused on the
mechanical functioning of the body, like how the heart
and muscles work and move.
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History of Motion Capture
The Motion Capture began in late 1800’s when Etienne
Jules Marey and Eadweard Muybridge performed
motion studies on various animals and humans.
History of Motion Capture (Contd.)
Etinne Jules
Marey’s Motion
Capture Suit
Eadweard
Myubridge
•Historically, Motion
Capture in animated
movies was created
using the extension of
"ROTOSCOPING"
technique.
Rotoscoping is an animation
technique in which the
animators trace over liveaction film movement frame
by frame, for use in animated
films. The pre-recorded liveaction film images are
projected onto a frosted glass
panel and are re-drawn by an
animator. This project
equipment is called
rotoscope.
Tom Goes To The Mayor
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There are primarily five methods in
motion capture. They are :
Prosthetic (or Electromechanical)
Acoustic
Electromagnetic
Optical fiber
Optical
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Prosthetic Motion Capture
uses Potentiometers on the
aforementioned plastic
exoskeleton that an actor
must “wear”, and then act
out his or her movements.
This is very accurate and
transmits real-time data at a
far greater range than any
other technology.
A gypsy3 prosthetic suite
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Fiber Optic sensors
Rotation based on
transmitted light
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This approach has a central
magnet with several
receivers attached to the
actor’s body. The receivers
capture and record the actors
movements and save them
to the computer. This
motion capture method can
be hindered by nearby metal
objects if they are large
enough and depending on
the power of magnets being
used.
A suit with magnetic sensors
Acoustic Motion Capture uses audio transmitters on the actor’s
body that make a “clicking” sound when activated by
movement. Receivers measure the time it takes for the sound
to reach them and triangulate the data to indicate a point on a
3D plane. This method has a problem of audio interface that
effects the accuracy of the motion capture. And the other
disadvantages are as follows:
 Limited Rage
 Limited number of sensors
 Cables on body
•Reflective Markers
•Multiple Cameras that
digitize different views of
performance.
Inside-In
Motion Capture
Systems
Inside-Out
Outside-In
•Electromechanical
•Optical Fiber
•Electromagnetic
•Acoustic
•Optical
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Location should
move rigidly with
joints
Stay away from
bulging muscles
Production Pipeline
Sensor
Calibration
Compute the position
and orientation of
camera/transmitter
Mapping to
characters
Direct Mapping or
retargetting
Subject
Calibration
Place markers on body,
compute skeleton
structure(lengths of
links)
Convert to Joint
Angles
Occlusion and
correspondence problems
Record Movements
Marker positions (and
orientations) varying over
time
Marker Data
Cleanup
Occlusion and
correspondence problems
Details to be taken Care of at time of Motion Capture:
•What we need is
– Position and orientation of the root segment
– Joint angles
– Length of each link (is it possible ?)
– Skeleton connectivity
– Skin deformation
• The mocap system actually provides
– Marker positions on the skin, or
– The positions and orientations of markers
Types of Objects that can be had motion capturing
•Human whole body
•Portions of body
•Facial animation
•Animals
•Puppets
•Other objects
What is Captured ?
Skin Deformation:
References:
•Motion Capture- http://en.wikipedia.org/wiki/Motion_capture
•A Brief History of Motion Capture for Computer Character Animationhttp://www.siggraph.org/education/materials/HyperGraph/animation/character_
animation/motion_capture/history1.htm
•Computer Graphics World-
http://www.cgw.com/ME2/dirmod.asp?sid=&nm=&type=Publishing&mod=Publi
cations%3A%3AArticle&mid=8F3A7027421841978F18BE895F87F791&tier=4
&id=A8B4004315A84A5089255A2E366E2E78
•Motion Capture- What is it? - http://www.metamotion.com/motioncapture/motion-capture.htm
•ACCAD-Motion Capture Lab-Home, information and documentationhttp://accad.osu.edu/research/mocap/mocap_home.htm
References (contd..)
•Motion Capturehttp://www.postmagazine.com/ME2/dirmod.asp?sid=&nm=&type=Publishing&
mod=Publications::Article&mid=8F3A7027421841978F18BE895F87F791&tier
=4&id=C715B81DD6674D62BD666D304D2E8D0B
•Motion Capturehttp://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2005/Motion_Cap
ture_KHY6_DCL34/Motion_Capture.htm
•Practical Motion Capture in Everyday Surroundingshttp://www.youtube.com/watch?v=V0yT8mwg9nc
•Motion Capture- http://web.mit.edu/comm-forum/papers/furniss.html
•Motion Analysis Studios- http://www.mastudios.com/index.html
Any Questions ????????
Thanks !!!!