motion path editing

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



MotivationMotivation

Original Motion

New Path



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



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



Direction of PathDirection of Path



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



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!



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!



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.



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



Path MathematicPath Mathematicss Use Right-handed Y-up convention Place some extra transformations

above the character’s root



Timing of a MotionTiming of a Motion



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



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)



ResultResult



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。



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

motion path editing

Documents

motion capture path

motion path editingi3d

path direction

detailedit path

wellmotion path

kineticmotion path editing

single motion

direction of motion