Method and apparatus for simulating dynamic contact of objects

• US 20020161562A1
• Filed: 04/24/2002
• Published: 10/31/2002
• Est. Priority Date: 04/25/2001
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Telekinesys Research Limited (Microsoft Corporation)
• Inventors: Gross, Oliver, Liss, Thomas, Strunk, Oliver
• Granted Patent: US 7,353,149 B2
• Time in Patent Office: Days
• US Class Current: 703/6
• CPC Class Codes: G06T 13/20 3D [Three Dimensional] animation
• CPC Class Codes: G06T 2210/21 Collision detection, intersection

Abstract

Contact of rigid bodies is simulated with friction. A contact point is determined as a mid point between closest points on each body. An integrated relative velocity (IRV) vector is computed, and is minimised by applying forces to both bodies. If the IRV value exceeds a threshold the bodies are deemed to be sliding. Non-penetration constraint and friction values are determined in separate processes and the output of one is fed to the other.

Claims

1. A method carried out by a simulator for simulating contact of rigid body objects, at discrete intervals of time, the method comprising the steps of:

-

determining non-penetration constraint and friction values in separate processes, and

feeding back the output of each process as an input to the other process.

2. A method as claimed in claim 1, wherein fed back inputs are a new dynamic property for each contact point outputted by the non-penetration constraint process, and a force value required for non-penetration outputted by the friction process.

3. A method as claimed in claim 1, wherein the non-penetration constraint process is executed after the friction process.

4. A method as claimed in claim 1, wherein the values from both processes are fed to an integrator which moves the simulation forward by a time step.

5. A method as claimed in claim 4, wherein the force values from the non-penetration constraint process from the previous time step are stored and fed forward to the friction process in the next time step.

6. A method as claimed in claim 1, wherein a value of an integrated relative velocity vector is maintained throughout simulation, with a zero value at the initial point of contact.

7. A method as claimed in claim 6, wherein the friction process calculates a force required to reduce or eliminate errors accumulated in the integrated relative velocity vector.

8. A method as claimed in claim 7, wherein the simulator determines that there is sliding if the integrated relative velocity vector value exceeds a threshold.

9. A method as claimed in claim 8 wherein if the simulator determines that there is sliding it does not determine restoring force values.

10. A method as claimed in claim 9 wherein if the simulator breaks contact and determines a new contact point it sets the integrated relative velocity vector to zero.

11. A method as claimed in claim 1, wherein a friction process is executed for each of a plurality of subsets of contact points.

12. A simulator comprising means for performing a method as claimed in any preceding claim.

13. A computer program product comprising software code for performing the steps of any of claims 1 to 11 when executing on a digital computer.