1. CS 6353 Computer Graphics and Multimedia
Motion Capture By
Vanitha Kowdeed

2. 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

3. 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

4. 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 1800’s when Etienne Jules Marey and Eadweard Muybridge performed motion studies on various animals and humans.

5. History of Motion Capture (Contd.)
Etinne Jules Marey’s Motion Capture Suit
Historically, Motion Capture in animated movies was created using the extension of "ROTOSCOPING" technique.
Eadweard Myubridge

6. 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

7. Motion Capture Technologies:
There are primarily five methods in motion capture. They are :
Prosthetic (or Electromechanical)
Acoustic
Electromagnetic
Optical fiber
Optical

8. 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

9. Optical Fiber Motion Capture:
Fiber Optic sensors
Rotation based on transmitted light

10. Electromagnetic Motion Capture:
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

11. Acoustic Motion Capture:
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

12. Optical Motion Capture:
Reflective Markers
Multiple Cameras that digitize different views of performance.

13. Motion Capture Systems
Electromechanical
Inside-In
Optical Fiber
Motion Capture Systems
Inside-Out
Electromagnetic
Acoustic
Optical
Outside-In

14. Marker Placements: Location should move rigidly with joints
Stay away from bulging muscles

15. Convert to Joint Angles
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

16. 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

17. Types of Objects that can be had motion capturing
Human whole body
Portions of body
Facial animation
Animals
Puppets
Other objects

18. What is Captured ?
Skin Deformation:

19. Examples:

20. References:
Motion Capture-
A Brief History of Motion Capture for Computer Character Animation-
Computer Graphics World-
Motion Capture- What is it? -
ACCAD-Motion Capture Lab-Home, information and documentation-

21. References (contd..)
Motion Capture-
Practical Motion Capture in Everyday Surroundings-
Motion Capture-
Motion Analysis Studios-

22. Any Questions ????????

23. Thanks !!!!