Motion Path Motion Path EditingEditing
I3D 2001I3D 2001
Speaker: AlvinSpeaker: Alvin
Date: 5/31/04Date: 5/31/04
Alivn/GAME Lab./CSIE/NDHU
2Motion Path Editing
OutlineOutline
OverviewOverview PathPath WhatWhat WhyWhy DetailDetail Evaluation FormEvaluation Form ConclusionConclusion
Alivn/GAME Lab./CSIE/NDHU
3Motion Path Editing
MotivationMotivation
Original Motion
New Path
Alivn/GAME Lab./CSIE/NDHU
4Motion Path Editing
AbstractAbstract 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 A simple extension to Motion
Displacement Mapping (1995) methodsDisplacement Mapping (1995) methods Provide better control (interactive Provide better control (interactive
manipulation)manipulation) Easy to implementEasy to implement Avoid violation of geometric constraintsAvoid violation of geometric constraints
Alivn/GAME Lab./CSIE/NDHU
5Motion Path Editing
What is a Path?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 PathDirection of Path
Alivn/GAME Lab./CSIE/NDHU
7Motion Path Editing
What is Path Editing?What is Path Editing?
Factor Motion intoFactor Motion intoPath And DetailPath And Detail
Edit Path as Edit Path as NeededNeeded
(use curve editing (use curve editing tools)tools)
Apply Detail toApply Detail tonew Pathnew Path
Alivn/GAME Lab./CSIE/NDHU
8Motion Path Editing
Why uses Path Editing?Why uses Path Editing?
Can’t Capture All PossibilitiesCan’t Capture All Possibilities Can’t Synthesize All StylesCan’t Synthesize All Styles Current Editing Tools Don’t ApplyCurrent Editing Tools Don’t Apply Sculpting motion interactively! Easy to implement tools!
Alivn/GAME Lab./CSIE/NDHU
9Motion Path Editing
Why not Motion Why not Motion Warping?Warping?
Treat each individual frame Treat each individual frame separatelyseparately
Can’t not maintain the relationship Can’t not maintain the relationship between path direction and between path direction and orientation over an entire orientation over an entire character’s motioncharacter’s motionPath Editing is a special purpose variant of Motion Warping!
Alivn/GAME Lab./CSIE/NDHU
10Motion Path Editing
Why not Constraint-Based Why not Constraint-Based Editing?Editing?
Enforce geometric details during Enforce geometric details during editsedits
Has not considered large scale Has not considered large scale control of directioncontrol of direction
Hard to implement wellHard to implement well
Motion Path Editing optionally uses constraints to clean up problems.
Alivn/GAME Lab./CSIE/NDHU
11Motion Path Editing
Path Path AbstractionAbstraction Use the character’s center of massUse the character’s center of mass
When dealing with two characters When dealing with two characters moving together, we choose the moving together, we choose the average position of the two charactersaverage position of the two characters
Fit “smooth” spline Compute a least-squares fit of a Compute a least-squares fit of a
piecewise polynomial curvepiecewise polynomial curve Space the knots equally in arc-Space the knots equally in arc-
length, rather than in timelength, rather than in time
Alivn/GAME Lab./CSIE/NDHU
12Motion Path Editing
Path MathematicPath Mathematicss 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 MotionTiming of a Motion
Alivn/GAME Lab./CSIE/NDHU
14Motion Path Editing
Arc-Length ParametrizationArc-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
ConstraintsConstraints
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
ResultResult
Alivn/GAME Lab./CSIE/NDHU
17Motion Path Editing
Evaluation FormEvaluation Form
論文簡報部份論文簡報部份 完整性介紹完整性介紹 (3)(3) 系統性介紹系統性介紹 (4)(4) 表達能力表達能力 (3)(3) 投影片製作投影片製作 (4)(4)
論文審閱部分論文審閱部分 瞭解論文內容瞭解論文內容 (3)(3) 結果正確性與完整性 結果正確性與完整性 (3)(3) 原創性與重要性原創性與重要性 (4)(4) 讀後啟發與應用: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
ConclusionConclusion
Edit overall path without changing detailsEdit overall path without changing details Permit a single motion to be applied in a wPermit a single motion to be applied in a w
ide variety of settingside variety of settings Simple to implementSimple to implement Provide the interactive tool for motion editProvide the interactive tool for motion edit
inging Maintain key features in the original motioMaintain key features in the original motio
nn Fail for motion that are highly kineticFail for motion that are highly kinetic