Maintaining the groom

• US 7,884,826 B1
• Filed: 05/25/2007
• Issued: 02/08/2011
• Est. Priority Date: 06/08/2006
• Status: Active Grant

• Current Assignee: Pixar (The Walt Disney Company)
• Original Assignee: Pixar (The Walt Disney Company)
• Inventors: Baraff, David
• Primary Examiner(s): Hajnik; Daniel F
• Application Number:
  US11/753,891
• Time in Patent Office: 1,355 Days
• Field of Search: None
• US Class Current: 345/473
• CPC Class Codes: G06T 13/40 of characters, e.g. humans, animals or virtual beings

Abstract

Methods and apparatus are disclosure for maintaining realistic grooming of simulated objects. In a method for simulating objects, a reference shape associated with a simulated object is received. A predetermined orientation is also received. A force acting on the simulated object is then modified based on the predetermined orientation. The force acts on the simulated object to shape the simulated object according to the reference shape. The force may be “strategically weakened” when the simulated object (or a portion thereof) is substantially aligned with the predetermined orientation. In a further method for simulating objects, a measured height associated with the simulated object is received. A “lifting” force is generated to reduce a difference between the measured height and a predetermined height associated with the reference shape. The lifting force simulates structure and internal forces that provide volume and shaping to physical objects, such as hair.

Claims

1. A method performed by one or more computer systems configured for simulating objects, the method comprising:

receiving, at the one or more computer systems, a reference shape associated with an object, wherein motions and positions of the object are determined by computer simulations of the object according to the reference shape and any influences external to the object considered by the computer simulations;

receiving, at the one or more computer systems, information specifying a predetermined orientation;

determining, with one or more processors associated with the one or more computer systems, that the object satisfies the predetermined orientation when a portion of the object is substantially aligned with the predetermined orientation;

modifying, with the one or more processors associated with the one or more computer systems, a first set of forces determined to be acting on the object by a computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the object is substantially aligned with the predetermined orientation; and

generating, with the one or more processors, information specifying a first position for the object resulting from the modified first set of forces, the first position being different from a second position resulting from the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation.

2. The method of claim 1 wherein modifying, with the one or more processors associated with the one or more computer systems, the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the simulated object is substantially aligned with the predetermined orientation comprises relaxing at least one force determined to be acting on the object by the computer simulation according to the reference shape.

3. The method of claim 1 wherein modifying, with the one or more processors associated with the one or more computer systems, the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the first object by the computer simulation when the portion of the simulated object is substantially aligned with the predetermined orientation comprises weakening at least one force determined to be acting on the object by the computer simulation in response to a difference between a measured orientation of the object and the predetermined orientation.

4. The method of claim 1 wherein modifying, with the one or more processors associated with the one or more computer systems, the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the object is substantially aligned with the predetermined orientation comprises adjusting a spring constant associated with a torsion force.

5. The method of claim 1 wherein the predetermined orientation is relative to a gravitational force.

6. The method of claim 1 wherein the predetermined orientation is relative to local acceleration.

7. The method of claim 1 wherein the predetermined orientation is substantially vertical.

8. The method of claim 1 further comprising:

receiving, at the one or more computer systems, a measured height associated with the object;

determining, with the one or more processors associated with the one or more computer systems, that the measured height is less than a predetermined height associated with the reference shape; and

generating, with the one or more processors associated with the one or more computer systems, a second set of forces to act on the object while the measured height is less than the predetermined height to attempt to reduce a difference between the measured height and the predetermined height, the second set of forces being different from the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation.

9. The method of claim 8 wherein the second set of forces acts on the object to move a current height associated with the object toward the predetermined height.

10. The method of claim 8 wherein the measured height associated with the object is determined relative to a portion of the object.

11. The method of claim 1 wherein the object comprises a hair object.

12. The method of claim 1 wherein the object comprises a linear object.

13. A non-transitory computer-readable medium storing computer-executable code for simulating objects, the computer-readable medium comprising:

code for receiving a reference shape associated with an object, wherein motions and positions of the object are determined by computer simulations of the object according to the reference shape and any influences external to the object considered by the computer simulations;

code for receiving information specifying a predetermined orientation;

code for determining that the object satisfies the predetermined orientation when a portion of the object is substantially aligned with the predetermined orientation;

code for modifying a first set of forces determined to be acting on the object by a computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the object is substantially aligned with the predetermined orientation; and

code for generating information specifying a first position for the object resulting from the modified first set of forces, the first position being different from a second position resulting from the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation.

14. The computer-readable medium of claim 13 wherein the code for modifying the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the object is substantially aligned with the predetermined orientation comprises code for relaxing at least one force determined to be acting on the object by the computer simulation according to the reference shape.

15. The computer-readable medium of claim 13 wherein the code for modifying the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the object is substantially aligned with the predetermined orientation comprises code for weakening at least one force determined to be acting on the object by the computer simulation in response to a difference between a measured orientation of the object and the predetermined orientation.

16. The computer-readable medium of claim 13 wherein the code for modifying the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the first object by the computer simulation when the portion of the simulated object is substantially aligned with the predetermined orientation comprises adjusting a spring constant associated with a torsion force.

17. The computer-readable medium of claim 13 wherein the predetermined orientation is relative to a gravitational force.

18. The computer-readable medium of claim 13 wherein the predetermined orientation is relative to local acceleration.

19. The computer-readable medium of claim 13 wherein the predetermined orientation is substantially vertical.

20. The computer-readable medium of claim 13 further comprising:

code for receiving a measured height associated with the object;

code for determining that the measured height is less than a predetermined height associated with the reference shape; and

code for generating a second set of forces to act on the object while the measured height is less than the predetermined height to attempt to reduce a difference between the measured height and the predetermined height, the second set of forces being different from the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation.

21. The computer-readable medium of claim 20 wherein the second set of forces acts on the object to move a current height associated with the object toward the predetermined height.

22. The computer readable medium of claim 20 further comprising:

code for determining the measured height associated with the object relative to a portion of the object.

23. The computer-readable medium of claim 13 wherein the object comprises a hair object.

24. The computer-readable medium of claim 13 wherein the object comprises a linear object.

25. A system for simulating objects, the system comprising:

a processor; and

a memory coupled to the processor, the memory configured to store a set of instructions which when executed by the processor configure the processor to;

receive a reference shape associated with an object, wherein motions and positions of the object are determined by computer simulations of the object according to the reference shape and any influences external to the object considered by the computer simulations;

receive information specifying a predetermined orientation;

determine that the object satisfies the predetermined orientation when a portion of the simulated object is substantially aligned with the predetermined orientation;

modify a first set of forces determined to be acting on the object by a computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the object is substantially aligned with the predetermined orientation; and

generate information specifying a first position for the object resulting from the modified first set of forces, the first position being different from a second position resulting from the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation.

26. The system of claim 25 wherein the processor is configured to relax at least one first force determined to be acting on the object by the computer simulation according to the reference shape to modify the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the object is substantially aligned with the predetermined orientation.

27. The system of claim 25 wherein the processor is configured to weaken at least one the first force determined to be acting on the object by the computer simulation in response to a difference between a measured orientation of the object and the predetermined orientation to modify the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the object by the computer simulation when the portion of the object is substantially aligned with the predetermined orientation.

28. The system of claim 25 wherein the processor is configured to adjust a spring constant associated with a torsion force to modify the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation while the object satisfies the predetermined orientation by relaxing at least one force in the first set of forces determined to be acting on the portion of the first object by the computer simulation when the portion of the simulated object is substantially aligned with the predetermined orientation.

29. The system of claim 25 wherein the predetermined orientation is relative to a gravitational force.

30. The system of claim 25 wherein the predetermined orientation is relative to local acceleration.

31. The system of claim 25 wherein the predetermined orientation is substantially vertical.

32. The system of claim 25 wherein the processor is further configured to:

receive a measured height associated with the object;

determine that the measured height is less than a predetermined height associated with the reference shape, and

generate a second set of forces to act on the object while the measured height is less than the predetermined height to attempt to reduce a difference between the measured height and the predetermined height, the second set of forces being different from the first set of forces determined to be acting on the object by the computer simulation according to the reference shape and any influences external to the object considered by the computer simulation.

33. The system of claim 32 wherein the processor is configured to generate the second set of forces to act on the object to move a current height associated with the object toward the predetermined height.

34. The system of claim 32 wherein the processor is configured to determine the measured height associated with the object relative to a portion of the object.

35. The system of claim 25 wherein the object comprises a hair object.

36. The system of claim 25 wherein the object comprises a linear object.