Rope / Belt start to jitter

Development Asset Creation
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1

Hi Support!

I’ve created a skeletal mesh of a 3m belt with 60 bones in it. I didn’t want to use the cable option in Unreal, because of that particular mesh.

I’ve created a blueprint with it, in such a way that I could have a movable end and start of the rope, by adding a scene component A_Ctrl (start attachment point) and B_ctrl (attachment point) to it. I’ve added functionality for that. One thing I’ve done specific, is that I change the rotation depending on the position of A and B.

I’ve made a sequence now, “Test_3_Belts”, in which I have 3 belts, with a fixed A_ctrl and a B_attached to a sphere that is moving. When the rope is getting stretched (not all the way), it starts to jitter. To be able to see the belts, you have to be in playmode.

Why…?

I can imagine there are so many reasons why, but I’m getting a bit lost in physics and collision settings.

When disabling collision on all the bodies, I have the feeling it’s still happening.

When removing my rotation adjustments, it’s still happening. So, it must be something connected to the physical asset I think.

Linear and angular damping on the bodies is now “5”. Linear limits are locked, angular are set (and also have soft constraints) + an angular motor.

I’ve uploaded the project here:

https://www.dropbox.com/scl/fi/3ly5ol8uf7qyspqqqal9a/Pulse\_Tests.rar?rlkey\=ef90zy1tq5j2l9xs0zq3isdxe\&dl\=0

Would it be possible to take a look?

Thank you!

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2

Steps to Reproduce
Hi Support!

I’ve created a skeletal mesh of a 3m belt with 60 bones in it. I didn’t want to use the cable option in Unreal, because of that particular mesh.

I’ve created a blueprint with it, in such a way that I could have a movable end and start of the rope, by adding a scene component A_Ctrl (start attachment point) and B_ctrl (attachment point) to it. I’ve added functionality for that. One thing I’ve done specific, is that I change the rotation depending on the position of A and B.

I’ve made a sequence now, “Test_3_Belts”, in which I have 3 belts, with a fixed A_ctrl and a B_attached to a sphere that is moving. When the rope is getting stretched (not all the way), it starts to jitter. To be able to see the belts, you have to be in playmode.

Why…?

I can imagine there are so many reasons why, but I’m getting a bit lost in physics and collision settings.

When disabling collision on all the bodies, I have the feeling it’s still happening.

When removing my rotation adjustments, it’s still happening. So, it must be something connected to the physical asset I think.

Linear and angular damping on the bodies is now “5”. Linear limits are locked, angular are set (and also have soft constraints) + an angular motor.

I’ve uploaded the project here:

https://www.dropbox.com/scl/fi/3ly5ol8uf7qyspqqqal9a/Pulse\_Tests.rar?rlkey\=ef90zy1tq5j2l9xs0zq3isdxe\&dl\=0

Would it be possible to take a look?

Thank you!

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3

After further research, I’m concluding that something is wrong with the physical bodies on the underside of the belt… still taking a look into that.

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4

Hi Tim,

Long chains of constrained bodies are generally quite tough to get stable. From taking a quick look, I’d initially suggest you use skinning to keep a nice visual, and see how many bodies/constraints you can reduce this to before it loses the effect you are trying to achieve. That alone may get the stability you need, but if not, we can tweak some further settings.

Best

Geoff Stacey

Developer Relations

EPIC Games

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