André Gagalowicz Projet MIRAGES

INRIA - Rocquencourt - Domaine de Voluceau78153 Le Chesnay Cedex

E-Mail : Andre.Gagalowicz@inria.frTél : 01 39 63 54 08

TOWARDS VIRTUAL TRY-ON TECHNOLOGY

TABLE OF CONTENTSI. INTRODUCTIONII. CONTEXT

II.1. InputII.2. Output

III. SIMULATION PROCESSIII.1. Numerical model for textile materialIII.2. Scene creationIII.3. Evolution of the system over time

IV. RESULTSV. CONCLUSION

I. INTRODUCTION

Aim : Commercial software in order to buy garments through internet

Presentation restricted to the case of WOVEN textiles

Limitation to a planar surface approach

APPLICATION: VIRTUAL TRY-ON(+ VIRTUAL PROTOTYPING)

FUNDING: Big Contract from ANR RNTL (french government) for 3 years started

in April 2007

Partners:- TEMAT INDUSTRIES (3D scanner SYMCAD)- LA REDOUTE (biggest French garment distributor)- Nadina Corrado (Fashion designer)- ENSITM (French Institute specialist of the mechanics of textile)- INRIA (MIRAGES project; specialist in garment simulation)

Target: produce a first prototype

Textiles have a

NONLINEARBehaviour

HYSTERETIC

TENSION

0

100

200

300

400

500

600

0 2 4 6 8 10 12 14 16 18

warpweft

F

SHEAR

-8

-6

-4

-2

0

2

4

6

8

-10 -8 -6 -4 -2 0 2 4 6 8 10

warpweft

F

BENDING

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5

warpweft

M

K

II.1 InputII. CONTEXT

III.1 Numerical model for textile material

a) Classical mass/spring model (finite elements)

II.2 Output

Evolution of the system over time

- 3D data

- images

II. CONTEXT

III.1 Numerical model for textile materials

III.2 Creation of the scene

III.3 Evolution of the system over time

III. SIMULATION PROCESS

III.1 Numerical Model for Textile Material (continued)

b) Improved mass/spring model• Warp/Weft structure is preserved

• Mixture of bipolar springs (tension and shear) and quadripolar (angular) springs

III.1 Numerical model for textile material (continued)

c) 2D pattern Meshing

Industrial representation of 2D patterns

III.2 Creation of the scene

III.2.1. Scene description

III.2.2. Garment Confection

a) 2D patterns positioned AUTOMATICALLY around the numerical mannequin

b) Sewing of 2D patterns

c) Gravity is added

III-2-2 a: Automatic prepositioning of the garment

CRUCIAL for the application and VERY DIFFICULT

Our solution solves the problem GEOMETRICALLYThe 3D garment appears sewn around the body and with a

very small amount of spring deformations (.001 mm of average deformation)

The simulator is only used for the final tuning (tremendous reduction of the computing time)

How is it done ? THE 3D MANNEQUIN

Hypothesis :

• The body is standing

• The body has his legs and arms put apart symmetrically

LABELLING OF THE 2D PATTERN CONTROL POINTS

Example of information which must exist on the 2D pattern :In green, sewing lines

In red, measurement lines

Blue dots : 2D pattern control points

MAPPING OF THE 2D PATTERNS CONTROL POINTS ON THE BODY OF THE MANNEQUIN

Flat prepositioning of the 2D pattern :• 1st step : projection of the 3D points of the body (corresponding to the control points of the 2D patterns) on the YoZ plane of the mannequin• 2nd step : mapping of the 2D pattern mesh on the YoZ plane

III.2.2. b 2D pattern sewing

2D patterns are sewn along sewing edges

Remark : Ambiguïty of the sewing information on the pattern !

III.2.3. Blowing of the Garment around the body

III.3. Evolution of the system over time

III.3.1. Integration of the law of dynamics

III.3.2. Control of the nonlinearity, the viscosity model and of the hysteresis

III.3.3. Spatial coherence maintenance

III.3.1 Integration of the law of dynamics

• Fondamental law of dynamics

Fext = m. A + c v

• Implicit integration method (Baraff)• viscosity parameters measured from real textile

III.3.2 Control of the nonlinearity and of the hysteresis

• Nonlinear and hysteretical springs control the KES of textile

• Validation by simulating Kawabata tests

RESULTS ON THE CONTROL OF THE KES

INSURE THAT OUR MECHANICAL MODEL MIMICS PRECISELY REAL WARP/WEFT TEXTILE

DOES NOT CONTROL COMPRESSION

TENSION FITTING

0

100

200

300

400

500

600

0 0.02 0.04 0.06 0.08 0.1 0.12

Virtual measurePhysic measure

F

SHEAR FITTING

Real measure

Virtual measure

F

-10 -8 -6 -4 -2 0 2 4 6 8 10

-6

-4

-2

0

2

4

6

BENDING FITTING

-0.01

-0.008

-0.006

-0.004

-0.002

0

0.002

0.004

0.006

0.008

0.01

-250 -200 -150 -100 -50 0 50 100 150 200 250

M reelM mesure

M

K

EXPERIMENTAL DETERMINATION OF DAMPING PARAMETERS in THE EQUATION OF DYNAMICS: cV

AIM: obtain a total phisical control of the equation of

dynamics

Damping model (Rayleigh)

F = ( M + K) V• M : mass matrix

• K : stiffness matrix

and have never been computed precisely before.

Rayleigh’s damping model applied for fabric model

3 spring types => 3 stiffness matrices K.K = Kbnd + Ksh + Ktns

Bending Shearing Tensile

Rayleigh's Model => Fdamp=( M+bnd Kbnd+sh Ksh+tns Ktns) V

Identification of Rayleigh’s model parameters(1)

Identification of Rayleigh’s model parameters(2)

Real fall down

Global Minimization

Ferror=MA-MG-Fsprings-Fdamp

Minimizing ||Ferror || by differentiatingLinear system : A ( bnd sh tns)T =b

Numerically A is ill-conditioned => the solution is not stable

Use of an iterative minimization algorithm

RESULT: Comparison between the real and the virtual FREE-FALL in the VISCOUS part of

the trajectory

III.3.3 Spatial coherence maintenance

• Detection of collisions

• Response to collisions

(done implicitly by the integration scheme)

Detection of Collisions• Optimisation through the use of bounding boxes

• Use of buckets

Response to Collisions: collision avoided IMPLICITELY (BARAFF method)

Implementation

• SGI 02 Unix Workstation• C++• Tcl scripts for the scene configuration and kinematics

IV. RESULTS

V. CONCLUSIONNumerous soft objects have the same behaviour as textilesExample : Muscular tissues,…

Extension to the volumetric case is STRAIGHTFORWARD but requires HEAVY computations actually

SOME SIMULATION RESULTS

CONTINUED

BUCKLING MODELING

STUDY OF BUCKLING(REAL)

STUDY OF BUCKLING(SIMULATED)