Unwinding an elastic

I am currently making a movie of an elastic-powered car, and I’ve hit a snag. Modelling a wound-up (twisted) elastic band isn’t a problem, but animating it to unwind realistically is a challenge I don’t know how to do. I’ve tried using the proportional modelling tool to rotate some of the vertices of the elastic band and then applying mesh IPOs, but it doesn’t seem to work. Can anybody think of an easier way? Thanks

Ahh yes, an Elastic-powered car, wait, whats an…
Could you provide a pic, that whould help.

One end of the elastic is anchored to the car body, and the other end is attached to a wheel. When the wheel is wound up, the elastic twists. When put down, the elastic unwinds, driving the wheel.

I wouldn’t try do do it the way you are. I would just use
some thing like this.


And vertex key between the shapes required. I would use a bump map for the twisted part in the middle.
It is just too difficult to actually have the rubber band untwist.


for those animations most times you have a special plug in.
to simulate unwinde is a hell of keyframing.

the biggest problem is the rotation and the translation issue.
and to make the unwinde effect smooth as well.

you could go eather the hard way and use a nurbs spline along which you extrude the elastic wire and animate the nurbs spline including rotation and translation. also since this happens very fast you might want to scipp the rotation effect and only work on the scale effect and use motion blure to hide you cheat.

or you could create a poly elastic wire and apply a sceleton into it which you animate. when you use IK this should work as well.

EDIT: here is a short animation and a blend file showing the keyframing
hope it might help.



Wow… thanks for all the replies! I’m going to look closer at the techniques mention here, especially that NURB spline dealy - that looks quite hardcore (thanks for the .blend file BTW).

i guess you could use hooks to do it.

hooks are new in 2.35, so go grab your self the new version

What you ask is very hard to do with current release


hooks? well that will make it even more difficult! imo