1. Biomechanically-Inspired Motion Path Editing Noah Lockwood and Karan Singh University of Toronto

2. Goals Fast editing of single motions High-level spatial direction Flexible to motion content

3. Related Work Path-based approaches – Motion graphs, motion doodles, deformable models Path-based motion editing – Kinematic, limited to walking or simple locomotion – Multi-character synchronized motion [Kim2009]

4. Algorithm Motion Preprocessing Interactive Path Deformation Pose Adjustment Timewarping

5. Terminology Keys: full body pose, position, and time Path: sequence of skeleton root positions

6. Algorithm Motion Preprocessing Interactive Path Deformation Pose Adjustment Timewarping

7. Motion Preprocessing Real motion changes are constrained Identify deformation handles Must correspond to potential motion changes

8. Motion Preprocessing Real motion changes are constrained Identify deformation handles Must correspond to potential motion changes Character exertion at path vertical minima

9. Motion Preprocessing Real motion changes are constrained Identify deformation handles Must correspond to potential motion changes Character exertion at path vertical minima Many local minima though:

10. Motion Preprocessing Real motion changes are constrained Identify deformation handles Must correspond to potential motion changes Character exertion at path vertical minima Many local minima though:

11. Path Deformation Handles Filter based on locally maximal # of contacts:

12. Algorithm Motion Preprocessing Interactive Path Deformation Pose Adjustment Timewarping

13. Interactive Path Deformation As-rigid-as-possible-deformation [Igarashi2005] – Adjustments for curves instead of triangle meshes Sharpness artifacts in large deformations:

14. ARAP Modifications Automatic pre-scaling factor:

15. Algorithm Motion Preprocessing Interactive Path Deformation Pose Adjustment Timewarping

16. Pose Adjustment Body rotation with path tangent Foot path deformation and IK

17. Algorithm Motion Preprocessing Interactive Path Deformation Pose Adjustment Timewarping

18. Unmodified timing can look unnatural:

19. Froude Number Used to evaluate dynamic similarity

20. Froude Number Used to evaluate dynamic similarity Relative stride length vs. Froude number:

21. Froude Timewarping Velocity and stride length ratios:

22. Froude Timewarping Velocity and stride length ratios: Target velocities and deformed path overconstrain new key times

23. Timewarping results

24. Algorithm Motion Preprocessing Interactive Path Deformation Pose Adjustment Timewarping

25. Algorithm Motion Preprocessing Interactive Path Deformation Pose Adjustment Timewarping Limited to simple edits of simple motion

26. Algorithm Motion Preprocessing Interactive Path Deformation Pose Adjustment Timewarping Limited to simple edits of simple motion Each stage modified based on components of motion

27. Vertical Motion ARAP deformation is 2D – Apply twice, from top and side

28. Vertical Motion ARAP deformation is 2D – Apply twice, from top and side Local coordinate system produces rotations:

29. Vertical Motion ARAP deformation is 2D – Apply twice, from top and side Local/global coordinate system produces shears:

30. Vertical Motion Editing Results

32. Ballistic Motion Unrealistic deformation of airborne motion:

33. Ballistic Motion Unrealistic deformation of airborne motion: Constrained to stretch only, no bending:

34. Ballistic Motion Editing Results Acceleration-based timewarping:

35. Ballistic Motion Editing Variety

36. Turns Realistic turning paths, but motion is too fast:

37. Curvature and Velocity One-third power law which relates curvature and velocity:

38. Curvature and Velocity One-third power law which relates curvature and velocity: Path curvature from curvature-continuous overall path

39. Path Curvature Overall path: handle-interpolating cubic spline

40. Path Curvature Overall path: handle-interpolating cubic spline

41. Turn Timewarping Curvature and velocity ratios:

42. Combined Timewarping Two target velocities from Froude and curvature rules:

43. Combined Timewarping Two target velocities from Froude and curvature rules: Multiplicative combination:

44. Combined Timewarp Results

45. Mixed Motion Editing

46. Non-human Characters

47. Simulation Editing

48. Conclusion and Discussion Our system: – Uses biomechanical models and observations – Accommodates many motion types – Automatically adjusts motion timing Limitations: – Acrobatic maneuvers – Range of plausible timings – Full-body editing

49. Thanks! Questions? Acknowledgements: – Jacobo Bibliowicz, Patrick Coleman, Martin de Lasa, John Hancock, Ryan Schmidt, Patricio Simari – SCA 2011 reviewers – CMU Motion Capture Database – Centroid Motion Capture – Autodesk

51. Pose Adjustment Rigid transformation of footsteps:

52. Pose Adjustment Rigid transformation of footsteps: