Question about the relationship between tension force and collision detection.

Hello,

Good question, but fortunately your sentence 'if two particles are parted from each other, the potential interaction will be deleted in the exact collision detection step' is false. The collision detection (...Collider... classes) does (almost) not care of deleting interactions. It is up to the Law2 to do this job and decide when to delete interactions. Then tensile forces can still exist when necessary !

For the second part of your question, the answer is yes. As you might understand it now, there is no difference between parted and overlapping spheres (the sign of normal force excepted), once the interaction exists.

Jérôme

Thank you for your answer!!
May I understand the calculation process as follows:
1. After generating particles, a quicksort is performed, and all the potential interactions are detected and saved;
2. At every simulation step, swaps between particle coordinates are detected. If an upper bound change to a lower bound in current axis, overlap along the other 2 axes is checked and if there is overlap along all axes, anew potential interaction is created. If a lower bound change to an upper bound, a real interaction(IGem or IPhy) should be checked. if there is only potential interaction, not IGem or IPhy, the interaction is deleted. But if there is a IGem or IPhy, the interaction will not be deleted. For example, if the normalCohesion parameter is set too big, so the impact range of tension force is very large, and a tension force exists between two parted particles although their AABB bound don't overlap.

That is to say, the creation of interaction is determined by collision detection, but the deletion of interaction is determined by both collision detection and real interaction(IGem or IPhy). Is that right?

At 2014-05-28 04:36:52, "Jérôme Duriez" <email address hidden> wrote:
>Your question #249399 on Yade changed:
>https://answers.launchpad.net/yade/+question/249399
>
> Status: Open => Answered
>
>Jérôme Duriez proposed the following answer:
>Hello,
>
>Good question, but fortunately your sentence 'if two particles are
>parted from each other, the potential interaction will be deleted in the
>exact collision detection step' is false. The collision detection
>(...Collider... classes) does (almost) not care of deleting
>interactions. It is up to the Law2 to do this job and decide when to
>delete interactions. Then tensile forces can still exist when necessary
>!
>
>For the second part of your question, the answer is yes. As you might
>understand it now, there is no difference between parted and overlapping
>spheres (the sign of normal force excepted), once the interaction
>exists.
>
>Jérôme
>
>--
>If this answers your question, please go to the following page to let us
>know that it is solved:
>https://answers.launchpad.net/yade/+question/249399/+confirm?answer_id=0
>
>If you still need help, you can reply to this email or go to the
>following page to enter your feedback:
>https://answers.launchpad.net/yade/+question/249399
>
>You received this question notification because you asked the question.

Thank you for your answer!!
May I understand the calculation process as follows:
1. After generating particles, a quicksort is performed, and all the potential interactions are detected and saved;
2. At every simulation step, swaps between particle coordinates are detected. If an upper bound change to a lower bound in current axis, overlap along the other 2 axes is checked and if there is overlap along all axes, anew potential interaction is created. If a lower bound change to an upper bound, a real interaction(IGem or IPhy) should be checked. if there is only potential interaction, not IGem or IPhy, the interaction is deleted. But if there is a IGem or IPhy, the interaction will not be deleted. For example, if the normalCohesion parameter is set too big, so the impact range of tension force is very large, and a tension force exists between two parted particles although their AABB bound don't overlap.

That is to say, the creation of interaction is determined by collision detection, but the deletion of interaction is determined by both collision detection and real interaction(IGem or IPhy). Is that right?

At 2014-05-28 04:36:52, "Jérôme Duriez" <email address hidden> wrote:
>Your question #249399 on Yade changed:
>https://answers.launchpad.net/yade/+question/249399
>
> Status: Open => Answered
>
>Jérôme Duriez proposed the following answer:
>Hello,
>
>Good question, but fortunately your sentence 'if two particles are
>parted from each other, the potential interaction will be deleted in the
>exact collision detection step' is false. The collision detection
>(...Collider... classes) does (almost) not care of deleting
>interactions. It is up to the Law2 to do this job and decide when to
>delete interactions. Then tensile forces can still exist when necessary
>!
>
>For the second part of your question, the answer is yes. As you might
>understand it now, there is no difference between parted and overlapping
>spheres (the sign of normal force excepted), once the interaction
>exists.
>
>Jérôme
>
>--
>If this answers your question, please go to the following page to let us
>know that it is solved:
>https://answers.launchpad.net/yade/+question/249399/+confirm?answer_id=0
>
>If you still need help, you can reply to this email or go to the
>following page to enter your feedback:
>https://answers.launchpad.net/yade/+question/249399
>
>You received this question notification because you asked the question.

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