emergent phantom wind-like force stemming from dynamic rope attachment

[gugiek]

Hi, 

I am having a weird issue with a rope connecting two objects. 

What I am trying to do:
I have a weighted balloon-like setup. One object is the weight, one the balloon. Both objects have a rigid body script and an attached script computes the buoyancy forces and adds the resulting forces in the update loop.
An undeformable rope should connect the two transferring the force of one to the other.

What I have tried:
Added a rope and connected the two ends to the objects with a dynamic particle attachment.

What is going wrong:
The forces acting on the system should only be up or down. A significant lateral force has appeared with the introduction of the dynamic attachment. The balloon seems now to be operating in a tornado.

Has a similar thing happened to anyone else? What other information should I share to make the problem clearer?

[josemendez]

Could it be that the rope is attached intersecting the balloon? This will result in jittering and/or ghost forces, because collisions and the attachment will fight each other: the rope can't simultaneously be inside the collider (as the attachment wants it to be) and outside the collider (as collisions want it to be).

This situation along with its solution, is described in the manual. See the last part of:
http://obi.virtualmethodstudio.com/tutor...aints.html

When pinning a particle very close to or inside a collider (so that they overlap), if you have collision constraints enabled you can encounter a situation in which both constraints fight each other. This results in jittering and/or an undesired offset in the pin position, because the collision and pin constraint cannot be met simultaneously. If the particle is pinned to a rigidbody, results will be even worse as this setup causes a force feedback loop with largely undefined behavior.