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Motion Capture Laboratory

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Motion Capture Laboratory School of Arts and Humanities ... Mocap system at UTD Vicon optical system - Best system in Academia! 8 high-speed MX 13 ... – PowerPoint PPT presentation

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Title: Motion Capture Laboratory


1
Motion Capture Laboratory
  • School of Arts and Humanities
  • Erik Jonsson School of Engineering and Computer
    Science
  • University of Texas at Dallas

2
What is Mocap?
  • The creation of a 3D representation of a live
    performance.Understanding Motion Capture for
    Computer Animation and Video Games by Alberto
    Menache.

3
Applications
  • Entertainment
  • Medicine
  • Arts / Education
  • Science / Engineering

4
Entertainment Live Action Films
  • Computer generated characters in live action
    films (e.g. Battle Droids and many others in Star
    Wars Prequels, Gullum in The Lord of the Rings,
    King Kong in King Kong)

5
Entertainment 3D computer animations
  • Characters in computer animated files (e.g. Polar
    Express, Monster House)

6
Entertainment Video Games
  • Video games by Electronic Arts, Gremlin, id,
    RARE, Square, Konami, Namco, and others, (e.g.
    Enemy Territory)

7
Medicine
  • Medicine (e.g., gait analysis, rehabilitation)
  • Sports medicine (e.g. injury prevention,
    performance analyses, performance enhancement)

Gait Analysis Service
8
Arts / Education
  • Dance and theatrical performances
  • Archiving (e.g., Marcel Marceau)

OSU/ACCAD
9
Science / Engineering
  • Computer Science (e.g., human motion database,
    indexing, recognitions)
  • Engineering (e.g., Biped robot developments)
  • Ergonomic product design
  • Military (e.g., field exercises, virtual
    instructors, and role-playing games)

10
Mocap animation
  • Motion capture animation is different from
    keyframe animation in terms of how motion is
    created.
  • Same principles apply to mocap animation
    keyframe animation!
  • A combination of motion capture animation and
    keyframe animation is often used.

11
Keyframe animation
  • A keyframe is a drawing of a key moment in an
    animated sequence, where the motion is at its
    extreme.
  • Inbetweens fill the gaps between keyframes.
  • Every motion is created by animators.

12
Advantages of mocap animation
  • Faster to create (only if an established
    production pipeline exists.)
  • Secondary motions and all the subtle motions are
    captured -gt more realism.
  • Physical interactions between performers and
    props can be captured.

13
Disadvantages of mocap animation
  • Cost.
  • Manipulating mocap data is often difficult -gt
    Re-capturing or key framing a shot with bad data
    is often easier.
  • Mapping mocap data of a performer to a character
    with a different proportion often causes problems.

14
Types of mocap equipment
  • Magnetic systems
  • Mechanical systems
  • Optical systems

15
Magnetic systems
  • Utilize sensors placed on the body to measure the
    magnetic field generated by a transmitter source.

16
Magnetic systems
  • ? Require no special lighting condition.
  • ? Sensors are never occluded.
  • X Require a metal-fee environment.

17
Mechanical systems
  • Exoskeleton with angle sensors.

18
Mechanical systems
  • ? Measure joint angles (no marker ID problems).
  • ? Sensors are never occluded.
  • X Breakable!
  • X Configuration of sensors is fixed.
  • X Constrains on joints.

19
Optical systems
  • The cameras are equipped with infrared LED's and
    filters. (Filters enhance the contrast of the
    image.)
  • The cameras see reflector markers.

20
Optical systems
  • ? Higher sampling rate.
  • ? Larger capture space.
  • X Markers are sometimes occluded -gt marker ID
    problems.
  • X Provide only positional data -gt joint angles
    need to be computed.

21
Mocap system at UTD
  • Vicon optical system - Best system in Academia!
  • 8 high-speed MX 13 (up to 1000 fps) and 8
    high-resolution MX 40 (4 million pixels) cameras.
  • Capture up to 5 performers at once.

22
Mocap system at UTD
  • Vicon optical system - Best system in Academia!
  • 8 high-speed MX 13 (up to 1000 fps) and 8
    high-resolution MX 40 (4 million pixels) cameras.
  • Capture up to 5 performers at once.

23
Production pipeline overview
  • Calibrate the system.
  • Fit a generic skeleton to the subjects
    proportion (subject calibration).
  • Capture shots reconstruct 3D trajectories using
    the calibrated subject.
  • Link the subject specific skeleton to a CG
    characters skeleton and edit motion (in
    MotionBuilder).
  • Add skin to the CG character, edit motion, and
    render (in Maya).Pipeline flow chart
    Detailed pipeline
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