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Motion Capture Laboratory
School of Arts and HumanitiesErik Jonsson School of Engineering and
Computer Science
University of Texas at Dallas
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.
Applications
• Entertainment
• Medicine
• Arts / Education
• Science / Engineering
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)
Entertainment: 3D computer animations
• Characters in computer animated files (e.g. Polar Express, Monster House)
Entertainment: Video Games
• Video games by Electronic Arts, Gremlin, id, RARE, Square, Konami, Namco, and others, (e.g. Enemy Territory)
Medicine
• Medicine (e.g., gait analysis, rehabilitation)• Sports medicine (e.g. injury prevention,
performance analyses, performance enhancement)
Gait Analysis Service
Arts / Education
• Dance and theatrical performances
• Archiving (e.g., Marcel Marceau)
OSU/ACCAD
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)
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.
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.
Advantages of mocap animation
• Faster to create (only if an established production pipeline exists.)
• Secondary motions and all the subtle motions are captured -> more realism.
• Physical interactions between performers and props can be captured.
Disadvantages of mocap animation
• Cost.
• Manipulating mocap data is often difficult -> 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.
Types of mocap equipment
• Magnetic systems
• Mechanical systems
• Optical systems
Magnetic systems
• Utilize sensors placed on the body to measure the magnetic field generated by a transmitter source.
Magnetic systems
Require no special lighting condition.
Sensors are never occluded.
• X Require a metal-fee environment.
Mechanical systems
• Exoskeleton with angle sensors.
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.
Optical systems
• The cameras are equipped with infrared LED's and filters. (Filters enhance the contrast of the image.)
• The cameras see reflector markers.
Optical systems
Higher sampling rate. Larger capture space.
• X Markers are sometimes occluded -> marker ID problems.
• X Provide only positional data -> joint angles need to be computed.
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.
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.
Production pipeline overview• Calibrate the system.• Fit a generic skeleton to the subject’s proportion
(subject calibration).• Capture shots & reconstruct 3D trajectories using the
calibrated subject.• Link the subject specific skeleton to a CG character’s
skeleton and edit motion (in MotionBuilder).• Add skin to the CG character, edit motion, and render
(in Maya).
Pipeline flow chart & Detailed pipeline
