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Motion Capture Laboratory

Motion Capture Laboratory. 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.

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Motion Capture Laboratory

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  1. Motion Capture Laboratory

  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 inKing 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 -> more realism. • Physical interactions between performers and props can be captured.

  13. 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.

  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-free 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 -> marker ID problems. • X Provide only positional data -> 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 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

  24. MOTION CAPTUREIN LIFE SCIENCES

  25. PREPARATION CAPTURE SPACE

  26. PREPARATION • PLACEMENT OF CAMERAS

  27. PREPARATION • BOUNDARY

  28. PREPARATION • Static calibration • This calculates the origin or centre of the capture volume and determines the orientation of the 3D Workspace. • Dynamic calibration • This involves movement of a calibration wand throughout the whole volume and allows the system to calculate the relative positions and orientations of the cameras. It also linearises the cameras.

  29. PREPARATION • Calibration procedure To perform the calibration: • Place the L-Frame on the floor in the centre of the capture volume • Select System | Live Monitors • Check that each camera is viewing only the four markers on the L-Frame

  30. PREPARATION • How good is the calibration? Residual for each Camera • A residual is a measure of the accuracy of a single camera1. They are larger the greater the distance of the camera from the capture volume and are measured in millimetres. What are acceptable residual values? • Residuals should be less than 0.1% of the distance from the camera to the centre of the capture volume. For example in a capture space of dimensions 10_10_3 meters, using MCams with 12.5mm lenses you would expect residuals in the range 1 to 4mm.

  31. PREPARATION Waving the wand There is no particular wand waving technique you should follow. You should, however, use the suggestions below as a guideline. • Allow the cameras to view the wand in multiple orientations, e.g., horizontal and vertical • Fill the capture volume completely • Medium pace of movement • Do not point the wand directly at any camera

  32. PREPARATION What are markers? Markers are the spheres that reflect light from the strobe back into the camera. Markers come in various shapes and sizes, for example: • 3mm hemispheres or 4mm spheres for facial and hand capture • 9 or 14mm spheres for full body capture • 12 or 20mm soft markers for capture when performing moves involving contact • 25, 35 and 50mm spheres for capturing movements in very large volumes

  33. PREPARATION

  34. DATABASE • ECLIPSE

  35. DATABASE

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