Help Obi Rope getting saggy on reducing scale

[abhilashca]

Hello,

I am using ObiRope as wire that's coming from the battery.

Prior to using, I created a sample obi rope example for wire material with 2 spheres at the end. The behavior of rope was as expected. (Attachment: rope-scale-default.jpg).

Since, the battery wire is of smaller size, I adjusted the scale of the obi rope component inside obi solver in the hierarchy. After this, the obi rope is showing as hanging wire. (Attachment: rope-scale-down-issue-1.jpg, rope-scale-down-issue-2.jpg)

If I change the scale back to 1 in obi rope component, then everything appears to be working fine.

Did anyone faced the same issue earlier? How can I resolve the same? Is there any values in inspector which I can tweak to fix this?

Any help will be appreciated.

Thanks in advance.

[josemendez]

Hi there,

When scaled, deformable object do not behave as rigid objects. This is because scaling is an affine transform, and it just does not make any sense to scale a deformable object. Affine transforms only work with rigid objects.

Think about it: if you had a straight rope along the X axis, you can scale it in the X axis to make it shorter. Now say the rope bends upwards in a 90º degree angle in the middle. What should happen when scaling along the X axis? only the part of the rope that's still aligned with the axis gets scaled? maybe the other half gets thinner? should the entire rope reduce its length? but that's no longer scaling just the X axis, since half of the rope is also being scaled in the Y axis right?.

Mathematically speaking you can't scale deformable objects (ropes, cloth, softbodies, etc). Only rigids.

You have two options here: just make the rope physically shorter/thinner (by using edit path mode), or scale the entire simulation space (by scaling the solver).

kind regards,

[abhilashca]

Thank you for the response and explaining the scenario using an example. Much appreciated.

Let me give a try with the options you have suggested. Will keep you posted.