Motion Path Editing I3D 2001 Speaker: Alvin Date: 5/31/04

Alivn/GAME Lab./CSIE/NDHU 2Motion Path Editing Outline Overview Overview Path Path What What Why Why Detail Detail Evaluation Form Evaluation Form Conclusion Conclusion

Alivn/GAME Lab./CSIE/NDHU 3Motion Path Editing Motivation Original MotionNew Path

Alivn/GAME Lab./CSIE/NDHU 4Motion Path Editing Abstract Two ways to create a range of motions using motion capture data: Capture all desired motions Alter a base motion to meet the desired needs A simple extension to Motion Displacement Mapping (1995) methods A simple extension to Motion Displacement Mapping (1995) methods Provide better control (interactive manipulation) Provide better control (interactive manipulation) Easy to implement Easy to implement Avoid violation of geometric constraints Avoid violation of geometric constraints

Alivn/GAME Lab./CSIE/NDHU 5Motion Path Editing What is a Path? An abstraction of the positional movement of a character A time-varying space curve whose value is related to the position of the character at a given time Encodes the direction of motion, which is different from, but related to, the orientation of the character A moving coordinate system Simplifying the character to a single point

Alivn/GAME Lab./CSIE/NDHU 6Motion Path Editing Direction of Path

Alivn/GAME Lab./CSIE/NDHU 7Motion Path Editing What is Path Editing? Factor Motion into Path And Detail Edit Path as Needed (use curve editing tools) Apply Detail to new Path

Alivn/GAME Lab./CSIE/NDHU 8Motion Path Editing Why uses Path Editing? Can ’ t Capture All Possibilities Can ’ t Capture All Possibilities Can ’ t Synthesize All Styles Can ’ t Synthesize All Styles Current Editing Tools Don ’ t Apply Current Editing Tools Don ’ t Apply Sculpting motion interactively! Easy to implement tools!

Alivn/GAME Lab./CSIE/NDHU 9Motion Path Editing Why not Motion Warping? Treat each individual frame separately Treat each individual frame separately Can ’ t not maintain the relationship between path direction and orientation over an entire character ’ s motion Can ’ t not maintain the relationship between path direction and orientation over an entire character ’ s motion Path Editing is a special purpose variant of Motion Warping!

Alivn/GAME Lab./CSIE/NDHU 10Motion Path Editing Why not Constraint-Based Editing? Enforce geometric details during edits Enforce geometric details during edits Has not considered large scale control of direction Has not considered large scale control of direction Hard to implement well Hard to implement well Motion Path Editing optionally uses constraints to clean up problems.

Alivn/GAME Lab./CSIE/NDHU 11Motion Path Editing Path Abstraction Use the character ’ s center of mass Use the character ’ s center of mass When dealing with two characters moving together, we choose the average position of the two characters When dealing with two characters moving together, we choose the average position of the two characters Fit “ smooth ” spline Compute a least-squares fit of a piecewise polynomial curve Compute a least-squares fit of a piecewise polynomial curve Space the knots equally in arc-length, rather than in time Space the knots equally in arc-length, rather than in time

Alivn/GAME Lab./CSIE/NDHU 12Motion Path Editing Path Mathematics Use Right-handed Y-up convention Place some extra transformations above the character ’ s root

Alivn/GAME Lab./CSIE/NDHU 13Motion Path Editing Timing of a Motion

Alivn/GAME Lab./CSIE/NDHU 14Motion Path Editing Arc-Length Parametrization Velocity is fixed Better maintain the dynamics of the motion Reduce the foot skate introduced by path transformation Keep arc-length the same

Alivn/GAME Lab./CSIE/NDHU 15Motion Path Editing Constraints Does not change the path, just the details Geometric constraint on end-effectors may specify either absolute or relative positions No guarantee that a constraint that exists over a duration of time will preserve any properties. Consistency Spacetime methods Per-frame IK plus filtering (PFIK+F)

Alivn/GAME Lab./CSIE/NDHU 16Motion Path Editing Result

Alivn/GAME Lab./CSIE/NDHU 17Motion Path Editing Evaluation Form 論文簡報部份 論文簡報部份 完整性介紹 (3) 完整性介紹 (3) 系統性介紹 (4) 系統性介紹 (4) 表達能力 (3) 表達能力 (3) 投影片製作 (4) 投影片製作 (4) 論文審閱部分 瞭解論文內容 (3) 結果正確性與完整性 (3) 原創性與重要性 (4) 讀後啟發與應用： 利用 Motion Capture 捕捉下來的資料，經過 Path Editing ，就可以產生新的動畫， 但可保留其細節，對於我們的研究蠻有幫助，我們可以改變武功招式動畫的 Path ， 這樣只需利用少許的資料，就可以產生出各種不同角度的對打招式。

Alivn/GAME Lab./CSIE/NDHU 18Motion Path Editing Conclusion Edit overall path without changing details Edit overall path without changing details Permit a single motion to be applied in a wide variety of settings Permit a single motion to be applied in a wide variety of settings Simple to implement Simple to implement Provide the interactive tool for motion editing Provide the interactive tool for motion editing Maintain key features in the original motion Maintain key features in the original motion Fail for motion that are highly kinetic Fail for motion that are highly kinetic