Bone Chain Stretching

Help
1

I’ve been experimenting with creating a simulation of a metal chain with a heavy ball attached to the end. The problem is that the chain keeps stretching as it falls or swings, more like rubber and less like solid metal.

Is there a setting that I’m missing that gets rid of this stretchiness? I’ve tried rotation stiffness and damping, but I feel like what I need is some sort of translation stiffness. But I don’t see a setting for that in Blender 4.3.

Any advice would be appreciated, thanks!

2

Hi @dwildDino, welcome to the forums! :partying_face:

A screenshot, or better yet a video, would help tremendously in cases such as these, and in almost all cases related to Ragdoll and feedback.

Without one, I would suspect an issue with mass ratios. Ragdoll is sensitive to very heavy things pulling on very light things, such as the scenario you described. To work around it, you have at least two options.

  1. Increase substeps, this gives the solver more time to figure things out, at a cost to performance
  2. Decreate mass ratio, for example by adjusting the density of that ball from 1.0 to 0.1 or 0.01. At an expense of realism, because now the ball will act less like a heavy ball.

Bottom line is, these scenarios are difficult for a physics solver to solve and needs more time to do it. You can also experiment with Position Iterations, both of which are located on the solver.

Hope it helps, do post visuals and we could help you further along.

3


Thanks for the response! Reducing density helped a lot. And increasing substeps reduced the jitter of the remaining bounce. I had been trying to reduce mass but reducing mass didn’t seem to change anything. What is the mass variable for?

I uploaded a video of the original issue. Now it is much better, thanks!

1 Like
4

Oh dear, yes that is pretty much an text-book impossible scenario for a rigid body solver. :sweat_smile: In mathematics, when demonstrating how poorly such solvers handle large mass ratios they typically use scenarios such as this.

Typically, mass is automatically computed based on the volume of each object and its Density property. Basically, mass = volume * density.

When Density = 0 then the Mass variable can be used to manually specify a mass. But, it’s typically not recommended because the reasonable masses you typically look for are those that relate to its volume. Anything else would not look consistent to its size.