Human Muscle Modeling using Generalized Cylinders for Volume Considerationss

1. Human Muscle Modeling using Generalized Cylinders for Volume Considerationss SK Semwal Bill Watson Debra McCullough University of Colorado, Colorado Springs

2. Topics of Presentation • Introduction and Background • Generalized Cylinders • Volume Considerations • Results • Conclusions

3. Introduction • Need: • Long standing research problem • Generalized cylinders: simple and intuitive • Volume considerations for muscles • Intersection with adjacent muscles/bones lead to suitable deformations

4. Previous Work • Since 1968 • Chen-Zeltzer - Biomechanical • Badler’s work – human body • Nadia and Daniel Thalmann – human body • Semwal and Dow’s GC Muscle models

5. Generalized Cylinders • Shani and Ballard • Set of cross sections • Set of generalized axis • Dow and Semwal • Model upper and lower arm using GCs

6. Extensions • Leg Musles • Polygons. NURBS, Shades choices • Animation sequences – leg exercises • Tension on the muscles • Speech recognition front-end • Models contraction/deformations using volume

7. Models • 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

8. Generalized Cylinders • Model 2D planar contours from Medical Books (Tortara, Gardner and Cated • Define these 2D planar contours along GC axis • NURBS defined using n points on contours • Rendered on SGI/OpenGL code

9. Intersection Testing and Intersection Resolution • Use cross sections • Move the intruding point away from the adjacent muscle/bones polygonal area between contours • Volume • 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

10. Deformation • 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

11. Results • Precise timing can be achieve • Smoothing introduces “lag”

12. Results

15. Summary • GC model provided a good method for modeling bones and muscles • Volume considerations allow good deformation effects • Biomechanical analysis and animation

16. Future Work • Model animations • Realistic biomechanical based rendering • Automatic detection from CT data and creating GCs

17. End