Motion Capture

• Keyframing complex actions (walking, etc) requires a lot of key frames.
• Instead, capture motion from real objects.

  Creatures and/or actors performing the desired motion.

• The positions of key points on the actor are tracked

  these motions are mapped to corresponding points in the model.

• May be necessary to generate secondary actions for the computer model.

  (tracking is expensive)

• Tracking technologies include
  1. Electromagnetic position and orientation sensors.
     • Requires a wire to each sensor.
     • Readings can be distorted by metal and magnetic fields.
     • Limited working volume.
  2. Ultrasonic rangefinder triangulation.
     • Cheaper but less accurate than magnetic sensors.
  3. Optical triangulation.
     • Reflective or emissive markers are attached to objects
     • Two cameras triangulate position
     • Can track more points cheaply, without wires
     • Points can be occluded.
  4. Body suit.
     • Fibers in instrumented clothing detect angles of all joints.
  5. Rotoscoping.
     • Arbitrary video from two cameras converted to motion paths
       • manual selection of key points
       • computer vision
     • Prone to error and occlusion.
     • Tedious if done manually.
  6. Puppetry.
     • Real-time data collected from an arbitrary input device
     • Mapped to an computer model, which is displayed in real time during capture.
     • A special-purpose input device in the shape of the object being animated may be built.