Dynamic Response for Motion Capture Animation

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					 Dynamic Response for Motion
     Capture Animation

        Victor B. Zordan
        Anna Majkowska
            Bill Chiu
         Matthew Fast
Riverside Graphics Lab University of
        California, Riverside

•   Introduction
•   Motion Selection
•   Transition Motion Synthesis
•   Implementation
•   Conclusion
• General adaptation and re-use of the data is
  limited by the available techniques for editing and
  modifying data in controllable ways.
• Physical models commonly used to responsivity to
  characters by generating modifications.
• But, the effects of an impact are over, there are
  no general schemes to move the simulation in a
  meaningful way and return the simulation to
  motion capture control.
• Automatically computes a dynamic reaction to an
  unanticipated impact and returns the character to
  an available motion from a capture repository for
  the remainder of the dynamic response to the
• Two critical components
   – Search engine compares initial simulated response with
     reaction segments from a motion library.
   – Joint-torque controller that actuates the simulation to
     reach the desired posture.
Motion Selection (Motion graphs)
• Creating response
   – Find transition-to motion capture sequence form
   – Compare simulated data with sequences in motion library.
• Define sample frame as vector:

• Distance D between windows is defined as:
• To capture the dynamic properties.
   – Assign high weights to the trunk parts.
   – Reduce the problem of sliding ground contact.
• To increase the efficiency of the search function
   – Pre-process database to find unique frames.
Transition Motion Synthesis
• Compute transition motion with two goals:
   – React in a physically plausible manner consistent with
     found motion.
   – Meet the desired state as closely as possible.
• Compute torques as
• [Zordan & Hodgins 2002] - Motion capture-driven
  simulations that hit and react.
• Timing is critical to make the character’s action
  appear realistic.
• Generating and blending motion capture data
   –   Interpolation to remove remaining disturbances.
   –   Interpolate linearly the root node offset.
   –   For rotation, interpolates by slerp quaternion.
   –   Using simple linear weighting.
• To create believable exchanges between
   – Heavy impact-based interactions require simulation of
     both the recipient and the deliverer of the impacts
• Simply following the completely simulated motion
  for a small number of frames after the impact.
• Then blending back to the same original motion
  through interpolation lead to a convincing attack
• Motion capture reactions
   – Pushed were made from the front, side and back with
     reaction including balanced recovery that required
     minimal foot repositioning.

• Range of such responses starting from a single
  pair of motion clips found by simply varying the
  facing direction of one of the characters.
• Takes advantage of the concept of the described
  burst following an impact without the need for a
  complicated implementation.
• Important contribution is use of a controller acts in
  accordance with the upcoming motion.
   – Avoid an unconscious look for the character.

Thanks for your listening