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Question About Rope Pulling
#1
Hi, 

I have a rope and attached rigidbodies to this rope's both ends.

I wanted to draw on the object on the left with pulling the object attached to the end of the rope(object on the right) very fast.
When I pull it slowly, the behaviour is as expected. But when I increase the pull speed it does not behave very well because of the stretching(I guess). I'm setting the mass of the object on the left very low(like 0.01) when pulling, but it couldn't solve the problem.

P.s: I pull the object with using it's rigidbody, not with it's transform.

I attached two screenshots to describe my problem. 

What settings should I apply to pull it correctly and very fast.

Thanks.


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#2
(01-02-2021, 05:11 PM)relevantname Wrote: Hi, 

I have a rope and attached rigidbodies to this rope's both ends.

I wanted to draw on the object on the left with pulling the object attached to the end of the rope(object on the right) very fast.
When I pull it slowly, the behaviour is as expected. But when I increase the pull speed it does not behave very well because of the stretching(I guess). I'm setting the mass of the object on the left very low(like 0.01) when pulling, but it couldn't solve the problem.

P.s: I pull the object with using it's rigidbody, not with it's transform.

I attached two screenshots to describe my problem. 

What settings should I apply to pull it correctly and very fast.

Thanks.

Physics simulations happen in discrete time steps or fixed duration,  so fast movements cause a lot of things to happen in very few time steps. Like most physics engines, Obi linearizes a lot of quantities, which means objects and particles are assumed to move in a straight line for the duration of each timestep. This assumption may not hold true if a lot of movement takes place in a single or very few time steps.

So a good way to improve quality and convergence speed is to reduce the timestep size. This will improve simulation on all fronts: less stretching, more accurate collision detection, etc. You can do this by either using more substeps in your ObiFixedUpdater (this chops up each timestep into multiple smaller time steps), or globally reducing the fixed timestep value in your Unity project (found in the Time settings). Here's an in-depth explanation of how the simulation is performed and how timestep length affects the results:
http://obi.virtualmethodstudio.com/tutor...gence.html


Let me know if this improves the result. cheers!
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