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Message #11228
[Bug 1301443] Re: Spheres/Box contact : spheres ori suddenly set to NaN.
** Changed in: yade
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/1301443
Title:
Spheres/Box contact : spheres ori suddenly set to NaN.
Status in Yet Another Dynamic Engine:
Fix Released
Bug description:
Hi,
Please see and launch the attached script.
Some spheres are falling into a box because of gravity. The simulation starts well, but when all particles are almost steady, wait for a few seconds and you will see that some of them who are in contact with the bottom wall will disapear. I spent some time to investigate and that's my preliminary conclusions :
- it is fully reproducible
- particles don't really disappear : their orientation is suddenly turned to Quaternion(Nan,Nan,Nan,2*pi). It's not linked with a high torque on them. All other attributes remains okay, and the other particles still can interact with it. If you manually set the orientation to a correct value after it disappears, it will appear again at the right place.
- you can reproduce this with one sphere (uncomment the last line of the script and comment the previous paragraph) : let it fall then apply to it a little angVel : "O.bodies[-1].state.angVel=(0.,0.,0.001)". It will disappear after a few timesteps.
- it's independent on the timestep value.
- it's dependant on the interpenetration of the contact : if you increase the gravity or decrease the young modulus, you will be able to avoid this behaviour.
Does somebody have an idea ? I think it's a rotation calculation
issue, in a very specific geometric case.
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References