Motion Path Editing

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

Outline • Overview • Path • What • Why • Detail • Evaluation Form • Conclusion Motion Path Editing

Motivation Original Motion New Path Motion 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 • Provide better control (interactive manipulation) • Easy to implement • Avoid violation of geometric constraints Motion 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 Motion Path Editing

Direction of Path Motion 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 Motion Path Editing

Why uses Path Editing? • Can’t Capture All Possibilities • Can’t Synthesize All Styles • Current Editing Tools Don’t Apply • Sculpting motion interactively! • Easy to implement tools! Motion Path Editing

Why not Motion Warping? • Treat each individual frame separately • 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! Motion Path Editing

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

Path Abstraction • Use the character’s center of mass • 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 • Space the knots equally in arc-length, rather than in time Motion Path Editing

Path Mathematics • Use Right-handed Y-up convention • Place some extra transformations above the character’s root Motion Path Editing

Timing of a Motion Motion 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 Motion 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) Motion Path Editing

Result Motion Path Editing

論文簡報部份 完整性介紹(3) 系統性介紹(4) 表達能力(3) 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： Evaluation Form 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。 Motion Path Editing

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

Motion Path Editing