Wrapping a bandage around a wrist? Looking for techniques/rig ideas.

Support Animation and Rigging
#1

I need to create an animation of a bandage being wrapped around a wrist. There are several factors making this very difficult, so I’m hoping someone might be able to suggest any techniques that might help.

First of all, this is being done for a medical animation, and there are strict requirements for how it will wrap, how tight it wraps, and that it does not slip once it is applied. I have experimented with using a cloth sim, but it breaks down too quickly for what I am trying to achieve. (Any slipping or wrap that is not tight is unacceptable, and there are also specifications on the tension being kept on the wrap while it is being applied. It also needs to unspool off the roll as it goes. This makes using the sim extremely difficult to hit all these targets.

here is an animation I found on youTube that does almost exactly what I need. https://www.youtube.com/watch?v=E5eqNvNPVLo

That animation is using a cloth sim, and even as decent as that looks, it is unacceptable for what I need to hit. (If you watch the animation, the bandage slides down the arm through the animation and on to the wrist.)

So,… anyone have any thoughts? This does not need to be done in one take,… I can cut the scene up into small chunks to make it work.

Thanks for looking!

#2

Hi,

I think you can do it with cloth simulation thanks to pinning with a variable weigth vertex group.
See http://wiki.blender.org/index.php/Doc:2.6/Manual/Modeling/Meshes/Vertex_Groups/Weight_Edit
You must create a vertex group and apply a weigth of 1 at the start. You assign this vertex group to the pinning section of the cloth simulation.
Then you rotate your bandage around the arm, decreasing the weigth (combined with the modifier ‘Vertex weigth edit’ ?) to make the little active section of the cloth out of the vertex group until it reach the arm, then increasing the weigth when the part of the cloth touches the arm
I did not test it at all, so hope it works and it is not a wrong direction.

#3

Thanks for the suggestion. At this point any ideas are in the right direction.

As for now, I’m all but giving up on using cloth, simply because of the control I need to have over it. I’m currently looking at using an armature that gets the mesh close to where it needs to be, followed by a shrinkwrap to get it on the surface. I’ve got some tests right now that are starting to look promising by using dynamic paint to set the weighting for the shrinkwrap. I wasn’t aware of the vertex weight modifiers you pointed out though, so I’m going to take a look and see if they can work better than dynamic paint for what I am doing here.

Thanks!