CSCI 520 Computer Animation and Simulation
Motion Capture
Jernej Barbic
University of Southern California
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What is Motion Capture?
• Motioncaptureistheprocessoftrackingreal- life motion in 3D and recording it for use in any number of applications.
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Why Motion Capture?
• Keyframes are generated by instruments measuring a human performer — they do not need to be set manually
• The details of human motion such as style, mood, and shifts of weight are reproduced with little effort
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Mocap Technologies: Optical
• Multiple high-resolution, high-speed cameras
• Light bounced from camera off of reflective markers
• High quality data
• Markers placeable anywhere
• Lots of work to extract joint angles
• Occlusion
• Which marker is which? (correspondence problem)
• 120-240 Hz @ 1Megapixel
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Facial Motion Capture
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Mocap Technologies: Electromagnetic
• Sensors give both position and orientation
• No occlusion or correspondence problem
• Little post-processing
• Limited accuracy
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Mocap Technologies: Exoskeleton
• Really Fast (~500Hz)
• No occlusion or correspondence problem
• Little error
• Movement restricted
• Fixed sensors
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Motion Capture
• Whynot?
– Difficult for non-human characters
• Can you move like a hamster / duck / eagle ? • Can you capture a hamster’s motion?
– Actors needed
• Which is more economical:
– Paying an animator to place keys – Hiring a Martial Arts Expert
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When to use Motion Capture?
• Complicatedcharactermotion
– Where “uncomplicated” ends and “complicated” begins is up to question
– A walk cycle is often more easily done by hand
– A Flying Monkey Kick might be worth the overhead of mocap
• Cananactorbetterexpresscharacter personality than the animator?
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