Method for simulating motion of cloth

• US 20060125830A1
• Filed: 06/29/2005
• Published: 06/15/2006
• Est. Priority Date: 06/30/2004
• Status: Active Grant

• Current Assignee: Warner Bros Entertainment Incorporated (Warner Bros. Discovery, Inc.)
• Original Assignee: Warner Bros Entertainment Incorporated (Warner Bros. Discovery, Inc.)
• Inventors: Piponi, Daniele Paolo David
• Granted Patent: US 7,385,603 B2
• Time in Patent Office: Days
• US Class Current: 345/473
• CPC Class Codes: G06T 13/20 3D [Three Dimensional] animation
• CPC Class Codes: G06T 2210/16 Cloth
• CPC Class Codes: G06T 2210/21 Collision detection, intersection

Abstract

A method for simulating motion of cloth or other flexible membranes corrects surface-to-surface intersection involving a membrane. The method may be applied at time intervals of a conventional motion simulation for computer-generated animation. When a collision is detected, a function for a line of intersection between intersecting surfaces is parameterized in terms of vertices of the membrane model. The function is differentiated, and a correction factor is applied to the dynamic simulation in proportion to the value of the partial derivative for respected ones of the intersected vertices. The correction factor may be smoothed over a number of vertices in the vicinity of the intersected vertices.

Claims

1. A method for simulating motion of a deformable thin membrane so as to correct surface-to-surface intersections involving the membrane, comprising:

modeling the deformable thin membrane as a tessellated surface comprising a plurality of vertices;

calculating modeled movement of the tessellated surface;

detecting collisions involving tessellations of the tessellated surface;

defining a function for a line of intersection resulting from a surface-to-surface collision detected in the detecting step;

differentiating the function to obtain a partial derivative with respect to ones of the plurality of vertices; and

applying a correction to the ones of the plurality of vertices in proportion to the partial derivative.

2. The method of claim 1, further comprising smoothing the correction over additional ones of the plurality of vertices.

3. The method of claim 2, wherein the smoothing step further comprises computing an average of the partial derivative over different ones of the plurality of vertices.

4. The method of claim 2, wherein the smoothing step further comprises computing the correction as a function of topological distance from the line of intersection.

5. The method of claim 2, wherein the line of intersection comprises a closed curve, and wherein the smoothing step further comprises computing the correction as a function of a topological distance from a centroid of the closed curve.

6. The method of claim 1, wherein the differentiating the function step further comprises using an automatic differentiation process.

7. The method of claim 1, wherein the applying the correction step further comprises associating a simulated correction force for application in the calculating step to respective ones of the plurality of vertices.

8. The method of claim 7, further comprising calculating the correction force by multiplying the partial derivative by a scalar value.

9. The method of claim 1, wherein the applying the correction step further comprises correcting positions of respective ones of the plurality of vertices.

10. The method of claim 9, wherein the applying the correction step further comprises calculating a corrective displacement for respective ones of the plurality of vertices by multiplying the partial derivative by a scalar value.

11. The method of claim 1, wherein the detecting step comprises detecting an intersection of the tessellated surface with itself.

12. The method of claim 1, wherein the detecting step comprises detecting an intersection of the tessellated surface with a surface of a separate model object.

13. A system for simulating motion of a deformable thin membrane so as to correct surface-to-surface intersections involving the membrane, comprising:

a computer operably associated with a memory, the memory holding program instructions for;

modeling the deformable thin membrane as a tessellated surface comprising a plurality of vertices;

calculating movement of the tessellated surface;

detecting collisions involving tessellations of the tessellated surface;

defining a function for a line of intersection resulting from a surface-to-surface collision detected in the detecting step;

differentiating the function to obtain a partial derivative with respect to ones of the plurality of vertices; and

applying a correction to the ones of the plurality of vertices in proportion to the partial derivative.

14. The system of claim 13, wherein the program instructions further comprise instructions for smoothing the correction over additional ones of the plurality of vertices.

15. The system of claim 14, wherein the program instructions for smoothing further comprise instructions for computing an average of the partial derivative over different ones of the plurality of vertices.

16. The system of claim 14, wherein the program instructions for smoothing further comprise instructions for computing the correction as a function of topological distance from the line of intersection.

17. The system of claim 14, wherein the program instructions for smoothing further comprise instructions for computing the correction as a function of a topological distance from a centroid of the line of intersection, wherein the line of intersection comprises a closed curve.

18. The system of claim 13, wherein the program instructions for differentiating further comprise instructions for differentiating the function using an automatic differentiation process.

19. The system of claim 13, wherein the program instructions for applying the correction further comprise instructions for associating a simulated correction force to respective ones of the plurality of vertices.

20. The system of claim 19, wherein the program instructions for applying the correction further comprise calculating the correction force by multiplying the partial derivative by a scalar value.

21. The system of claim 13, wherein the program instructions for applying the correction further comprise instructions for correcting positions of respective ones of the plurality of vertices.

22. The system of claim 13, wherein the program instructions for applying the correction further comprise instructions for calculating a corrective displacement for respective ones of the plurality of vertices by multiplying the partial derivative by a scalar value.

23. The system of claim 13, wherein the program instructions for applying the correction further comprise instructions for detecting an intersection of the tessellated surface with itself.

24. The system of claim 13, wherein the program instructions for applying the correction further comprise instructions for detecting an intersection of the tessellated surface with a surface of a separate model object.

25. A video sequence, comprising:

a plurality of graphic images arranged in a time sequence to depict motion of a deformable thin membrane, wherein at least a portion of the plurality of graphic images are prepared by;

modeling the deformable thin membrane as a tessellated surface comprising a plurality of vertices;

calculating modeled movement of the tessellated surface;

detecting collisions involving tessellations of the tessellated surface;

defining a function for a line of intersection resulting from a surface-to-surface collision detected in the detecting step;

differentiating the function to obtain a partial derivative with respect to ones of the plurality of vertices; and

applying a correction to the ones of the plurality of vertices in proportion to the partial derivative.

26. The video sequence of claim 25, wherein the plurality of graphic images are further prepared by smoothing the correction over additional ones of the plurality of vertices.

27. The video sequence of claim 25, wherein the plurality of graphic images are further prepared by, in the differentiating step, differentiating the function using an automatic differentiation process.

28. The video sequence of claim 25, wherein the plurality of graphic images are further prepared by, in the applying the correction step, associating a simulated correction force for application in the calculating step to respective ones of the plurality of vertices.

29. The video sequence of claim 25, wherein the plurality of graphic images are further prepared by, in the applying the correction step, correcting positions of respective ones of the plurality of vertices.

30. The video sequence of claim 25, wherein the plurality of graphic images are further prepared by, in the detecting step, detecting an intersection of the tessellated surface with itself.

31. The video sequence of claim 25, wherein the plurality of graphic images are further prepared by, in the detecting step, detecting an intersection of the tessellated surface with a surface of a separate model object.