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I have a soft body mesh and an armature.

  • I have one bone holding one end of the Soft body and another bone used to stretch the soft body.
  • I then want one of the bones to let go of the soft body so it springs back like a piece of elastic that has snapped.

You can animate the bone so it returns to the first position but this stops the mesh moving correctly.

Any ideas how this can be done?
It doesn't have to be an armature it could be empties, etc.

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    $\begingroup$ Could you please add your .blend file? $\endgroup$
    – stacker
    Sep 10, 2013 at 14:04

3 Answers 3

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Demo of what this does here:

enter image description here

I just had a quick play with this idea and got something pretty close.

  1. Create soft body.

  2. Create armature with two separate bones.

  3. Parent soft body to armature.

  4. Stretch the soft body by moving one of the bones.

  5. This is where it gets a bit limited, but apply the armature modifier as a shape key (I know, you're stuck with the amount of stretch at that point, but trust me, it has some effect and might help).

  6. Keyframe the value of the shape key so that it stetches out slowly over maybe 50 frames, then key it down at 0 about 5 frames later.

  7. Play the animation, and notice how the oscillation of the soft body seems to have been amplified by the quickly retracting shape key.

I really didn't think this would work at all, so having it do at least something made me quite pleased.

See what you can do with that.

I tried keying the deform influence of the bone on and off but that didn't have any effect as far as I could tell.

Nb. I used Automatic Weights. If you don't then there should be a weight painting step between 3 and 4.

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Thanks for the Answers.

I have used a combination of the two to produce the results I was after:

Instead of using an armature I produced the initial stretch using a shape key. I then key framed the value of the shape key over time from 0 - 1 - 0.

I then set the cache start frame of the soft body sim to the frame when the shape key was changing from 1 - 0.

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It seems that you already managed to stretch and contract the soft body by using the bones.

If you want to stop the motion suddenly you could set two keyframes on Goal Strength / Minimum first keyframe (Right mouse button / insert keyframe) with value 0 and second keyframe this value to .999

enter image description here

See also:

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