CS 6353 Computer Graphics and Multimedia

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CS 6353 Computer Graphics and Multimedia

• Motion Capture
• By
• Vanitha Kowdeed

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• Overview
• 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

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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
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Purpose of Motion Capture

• 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.
• History of Motion Capture
• The Motion Capture began in late 1800s when
  Etienne Jules Marey and Eadweard Muybridge
  performed motion studies on various animals and
  humans.

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History of Motion Capture (Contd.)

• Etinne Jules Mareys Motion Capture Suit

• Historically, Motion Capture in animated movies
  was created using the extension of "ROTOSCOPING"
  technique.

Eadweard Myubridge
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Rotoscoping

• Rotoscoping is an animation technique in
  which the animators trace over live-action film
  movement frame by frame, for use in animated
  films. The pre-recorded live-action 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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Motion Capture Technologies

• There are primarily five methods in
  motion capture. They are
• Prosthetic (or Electromechanical)
• Acoustic
• Electromagnetic
• Optical fiber
• Optical

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Prosthetic(or
Electromechanical) Motion Capture

• 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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Optical Fiber Motion Capture

• Fiber Optic sensors
• Rotation based on transmitted light

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Electromagnetic Motion Capture

• This approach has a central magnet with several
  receivers attached to the actors 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
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Acoustic Motion Capture

• Acoustic Motion Capture uses audio transmitters
  on the actors 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

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Optical Motion Capture

• Reflective Markers
• Multiple Cameras that digitize different views of
  performance.

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• Electromechanical

Inside-In

• Optical Fiber

Motion Capture Systems
Inside-Out

• Electromagnetic

• Acoustic
• Optical

Outside-In
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Marker Placements

• Location should move rigidly with joints
• Stay away from bulging muscles

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Production Pipeline
Sensor Calibration
Subject Calibration
Record Movements
Compute the position and orientation of
camera/transmitter
Place markers on body, compute skeleton
structure(lengths of links)
Marker positions (and orientations) varying over
time
Marker Data Cleanup
Convert to Joint Angles
Mapping to characters
Occlusion and correspondence problems
Direct Mapping or retargetting
Occlusion and correspondence problems
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• 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

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Types of Objects that can be had motion
capturing

• Human whole body
• Portions of body
• Facial animation
• Animals
• Puppets
• Other objects

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What is Captured ?
Skin Deformation
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Examples
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• References
• Motion Capture- http//en.wikipedia.org/wiki/Motio
  n_capture
• A Brief History of Motion Capture for Computer
  Character Animation-
• http//www.siggraph.org/education/materials/Hyp
  erGraph/animation/character_animation/motion_captu
  re/history1.htm
• Computer Graphics World-
•  
• http//www.cgw.com/ME2/dirmod.asp?sidnmtypePu
  blishingmodPublications3A3AArticlemid8F3A702
  7421841978F18BE895F87F791tier4idA8B4004315A84A
  5089255A2E366E2E78
• Motion Capture- What is it? - http//www.metamotio
  n.com/motion-capture/motion-capture.htm
• ACCAD-Motion Capture Lab-Home, information and
  documentation-
•  
• http//accad.osu.edu/research/mocap/mocap_ho
  me.htm

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• References (contd..)
• Motion Capture-
•  
• http//www.postmagazine.com/ME2/dirmod.asp?sidnm
  typePublishingmodPublicationsArticlemid8F
  3A7027421841978F18BE895F87F791tier4idC715B81DD
  6674D62BD666D304D2E8D0B
• Motion Capture-
•  
• http//instruct1.cit.cornell.edu/courses/ee476/Fin
  alProjects/s2005/Motion_Capture_KHY6_DCL34/Motion_
  Capture.htm
• Practical Motion Capture in Everyday
  Surroundings-
•  
• http//www.youtube.com/watch?vV0yT8mwg9nc
• Motion Capture- http//web.mit.edu/comm-forum/pape
  rs/furniss.html
• Motion Analysis Studios- http//www.mastudios.com/
  index.html

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Any Questions ????????
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Thanks !!!!