Moving Rope in 3.2 (Unity 2017.1.1)

[josemendez]

Hi Jose,

Thank you, that seems to have helped our teleporting issue. 

We are using Obi rope as a mechanical arm for our character and there is a pin set to his elbow's position so it maintains the shape of the arm. When the player is standing on a platform moving upwards, the arm jiggles a lot. In the previous version we seemed to solve this issue by checking the simulate in local space option which stopped the jiggling. 

Now when I tick simulate in local space, the pin behaves very strangely and it gets pushed further away from the player as the player gets further away from the world's origin. I suspect I am using this property incorrectly. Is there some other way I can stop it jiggling on moving platforms?

Hi there!

Pin constraints are best used together with rigidbodies, as they're meant to inject force back into the body they're pinned to. If your character has a rigidbody at its root this can be specially problematic in local space as it can induce a feedback loop, where the rope moves the character, and the character moves the rope, etc.

Use handles instead.

Edit: Tested a couple use cases with pin constraints. A local-space setup with a solver and a rigidbody at the root of the hierarchy, and colliders/ropes underneath them pinned together, causes the issue you mention, or at least a similar one (the rigidbody starts floating around in a strange fashion while the rope gets pushed far from it). If the rigidbody is not at the root of the hierarchy, it works as expected since the rope is no longer capable of altering its own reference frame.

You can either re-design the character hierarchy to break this feedback loop, or use fixed particles/handles (which are also far more performant than pin constraints).