Human Muscle Modeling Human Muscle Modeling using Generalized using Generalized

Cylinders for Volume ConsiderationssCylinders for Volume Considerationss

SK SemwalSK SemwalBill WatsonBill Watson

Debra McCulloughDebra McCulloughUniversity of Colorado, Colorado University of Colorado, Colorado

SpringsSprings

Topics of PresentationTopics of Presentation

Introduction and BackgroundIntroduction and Background Generalized CylindersGeneralized Cylinders Volume ConsiderationsVolume Considerations ResultsResults ConclusionsConclusions

Introduction Introduction

Need:Need: Long standing research problemLong standing research problem Generalized cylinders: simple and Generalized cylinders: simple and

intuitiveintuitive Volume considerations for musclesVolume considerations for muscles Intersection with adjacent Intersection with adjacent

muscles/bones lead to suitable muscles/bones lead to suitable deformationsdeformations

Previous WorkPrevious Work

Since 1968Since 1968 Chen-Zeltzer - BiomechanicalChen-Zeltzer - Biomechanical Badler’s work – human bodyBadler’s work – human body Nadia and Daniel Thalmann – human Nadia and Daniel Thalmann – human

bodybody Semwal and Dow’s GC Muscle modelsSemwal and Dow’s GC Muscle models

Generalized CylindersGeneralized Cylinders

Shani and Ballard Shani and Ballard Set of cross sectionsSet of cross sections Set of generalized axisSet of generalized axis

Dow and SemwalDow and Semwal Model upper and lower arm using GCsModel upper and lower arm using GCs

ExtensionsExtensions

Leg MuslesLeg Musles Polygons. NURBS, Shades choicesPolygons. NURBS, Shades choices

Animation sequences – leg exercisesAnimation sequences – leg exercises Tension on the musclesTension on the muscles Speech recognition front-endSpeech recognition front-end Models contraction/deformations using Models contraction/deformations using

volumevolume

ModelsModels

Femur or thigh bone – longest and Femur or thigh bone – longest and heaviest bone – hip to tibia heaviest bone – hip to tibia

Tibia or shin bone – next heavy bone Tibia or shin bone – next heavy bone transfers the weight to ankles from hiptransfers the weight to ankles from hip

Fibula – parallel to tibia on the outside Fibula – parallel to tibia on the outside lateral – attached to several muscles – lateral – attached to several muscles – acts a pulley to tendons behind ankleacts a pulley to tendons behind ankle

Generalized CylindersGeneralized Cylinders Model 2D planar contours from Medical Model 2D planar contours from Medical

Books (Tortara, Gardner and CatedBooks (Tortara, Gardner and Cated Define these 2D planar contours along GC axisDefine these 2D planar contours along GC axis NURBS defined using n points on contoursNURBS defined using n points on contours

Rendered on SGI/OpenGL codeRendered on SGI/OpenGL code

Intersection Testing and Intersection Testing and Intersection Resolution Intersection Resolution

Use cross sectionsUse cross sections Move the intruding point away from the Move the intruding point away from the

adjacent muscle/bones polygonal area adjacent muscle/bones polygonal area between contoursbetween contours

VolumeVolume Two cross sections Aavg = (Ai + Ai+1)/2 Two cross sections Aavg = (Ai + Ai+1)/2 Distance between the two GC-axis point for Distance between the two GC-axis point for

the two cross sectionsthe two cross sections Volume between two cross sections = Aavg * d Volume between two cross sections = Aavg * d Repeat for all cross sections pair for that GCRepeat for all cross sections pair for that GC

DeformationDeformation

pct_chg = (curr_vol - init_vol) / pct_chg = (curr_vol - init_vol) / init_volinit_vol

rel_chg = (cum_sum (curr_vol - rel_chg = (cum_sum (curr_vol - init_vol))/cum_suminit_vol))/cum_sum

rel_change acts as a guide based upon rel_change acts as a guide based upon tolerance in changing the cross tolerance in changing the cross section pointssection points

Points next to bone and other muscle Points next to bone and other muscle not modified not modified

ResultsResults

Precise timing can Precise timing can be achievebe achieve

Smoothing Smoothing introduces “lag”introduces “lag”

Results Results

Summary Summary

GC model provided a good method GC model provided a good method for modeling bones and muscles for modeling bones and muscles

Volume considerations allow good Volume considerations allow good deformation effects deformation effects

Biomechanical analysis and Biomechanical analysis and animationanimation

Future WorkFuture Work

Model animationsModel animations Realistic biomechanical based Realistic biomechanical based

renderingrendering Automatic detection from CT data Automatic detection from CT data

and creating GCsand creating GCs

End