Human Muscle Modeling using Generalized
Cylinders for Volume Considerationss
SK Semwal
Bill Watson
Debra McCullough
University of Colorado, Colorado Springs
Topics of Presentation
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Introduction and Background
Generalized Cylinders
Volume Considerations
Results
Conclusions
Introduction
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Need:
Long standing research problem
 Generalized cylinders: simple and intuitive
 Volume considerations for muscles
 Intersection with adjacent muscles/bones lead
to suitable deformations
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Previous Work
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Since 1968
Chen-Zeltzer - Biomechanical
 Badler’s work – human body
 Nadia and Daniel Thalmann – human body
 Semwal and Dow’s GC Muscle models
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Generalized Cylinders
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Shani and Ballard
Set of cross sections
 Set of generalized axis
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Dow and Semwal
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Model upper and lower arm using GCs
Extensions
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Leg Musles
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Polygons. NURBS, Shades choices
Animation sequences – leg exercises
Tension on the muscles
 Speech recognition front-end
 Models contraction/deformations using
volume
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Models
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Femur or thigh bone – longest and
heaviest bone – hip to tibia
Tibia or shin bone – next heavy bone
transfers the weight to ankles from hip
Fibula – parallel to tibia on the outside
lateral – attached to several muscles –
acts a pulley to tendons behind ankle
Generalized Cylinders
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Model 2D planar contours from Medical Books
(Tortara, Gardner and Cated
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Define these 2D planar contours along GC axis
NURBS defined using n points on contours
Rendered on SGI/OpenGL code
Intersection Testing and
Intersection Resolution
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Use cross sections
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Move the intruding point away from the adjacent
muscle/bones polygonal area between contours
Volume
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Two cross sections Aavg = (Ai + Ai+1)/2
Distance between the two GC-axis point for the two
cross sections
Volume between two cross sections = Aavg * d
Repeat for all cross sections pair for that GC
Deformation
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pct_chg = (curr_vol - init_vol) / init_vol
rel_chg = (cum_sum (curr_vol init_vol))/cum_sum
rel_change acts as a guide based upon
tolerance in changing the cross section
points
Points next to bone and other muscle not
modified
Results
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Precise timing can be
achieve
Smoothing introduces
“lag”
Results
Summary
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GC model provided a good method for
modeling bones and muscles
Volume considerations allow good
deformation effects
Biomechanical analysis and animation
Future Work
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Model animations
Realistic biomechanical based rendering
Automatic detection from CT data and
creating GCs
End