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Computer Animation Algorithms and Techniques

Computer Animation Algorithms and Techniques. Motion Capture. Rick Parent. Computer Animation. MoCap Technologies. The talent - the person whose motion is to be captured. Instrumentation - markers placed on the talent. From sensed markers, reconstruct skeleton of person.

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Computer Animation Algorithms and Techniques

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  1. Computer AnimationAlgorithms and Techniques Motion Capture Rick Parent Computer Animation

  2. MoCap Technologies The talent - the person whose motion is to be captured Instrumentation - markers placed on the talent From sensed markers, reconstruct skeleton of person Usually positional information is recorded, but accelerometers are also used New techniques allow for markerless motion capture Rick Parent Computer Animation

  3. “Traditional” MoCap Technologies • Optical – uses video capture • passive – markers just reflect light • active – markers emit light • Magnetic – markers sense their status in magnetic field • Electro-Mechanical – rotors connected to limb-aligned rods record their status – for hands, fiber-optic sensors are an option Rick Parent Computer Animation

  4. Optical - Active PhoeniX Technologies www.ptiphoenix.com Rick Parent Computer Animation

  5. Ascention technology http://www.ascension-tech.com/ Magnetic Rick Parent Computer Animation

  6. MetaMotion www.metamotion.com/metamotion.htm Electro-Mechanical Rick Parent Computer Animation

  7. Xsens http://www.xsens.com/en/general/mvn Inertial Rick Parent Computer Animation

  8. Passive Optical – most common Brent Haley at the Advanced Computing Center for Art and Design at Ohio State University Rick Parent Computer Animation

  9. Motion capture lab Multiple markers - e.g., 20-40 Multiple cameras - e.g., 8-14 high-res, high-speed Constrained, conditioned space - 20x20 non-reflective Multiple lights - synced w/ cameras Vicon http://www.vicon.com/applications/animation.html Rick Parent Computer Animation

  10. Processing the Images • Extract markers from video • Track markers over time in video • Marker cleanup • 3D marker position reconstruction • Joint position reconstruction • Joint angle reconstruction Rick Parent Computer Animation

  11. Extract markers from video • Basic image processing aided by constrained environment: • High contrast markers • Special illumination • Non-reflective environment Rick Parent Computer Animation

  12. Marker tracking Given frames each with recognized markers Associate markers over multiple frames • Temporal coherence using: • Position • Frame rate • Velocity Rick Parent Computer Animation

  13. Marker Clean-up Rick Parent Computer Animation

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  16. 3D – image plane projection Projecting marker onto image plane Rick Parent Computer Animation

  17. Camera calibration Project known 3-space points to camera’s image Six degrees of freedom - use that many known point-pairs Rick Parent Computer Animation

  18. Projecting from 2D image out to 3-space Rick Parent Computer Animation

  19. Reconstructing a 3D marker Rick Parent Computer Animation

  20. Markers Joint Fitting to the skeleton Locate joints relative to markers Rick Parent Computer Animation

  21. Reconstructing angles Rick Parent Computer Animation

  22. Mocap output See sample files http://accad.osu.edu/research/mocap/mocap_data.htm http://mocap.cs.cmu.edu/ Rick Parent Computer Animation

  23. Manipulating the mocap data Frequency deconstruction & manipulation Transitioning between two motions – Blending How to map a motion onto a figure with different geometry - Retargeting Finding motion clips to create behavior – motion graphs Rick Parent Computer Animation

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