# Rolling Up a Circle-Shaped Cloth Object That's Folded in Half

Hi all,

So, I’ve been chewing on this for a while, now. I’m doing an animation that depicts a circular piece of mylar, folded in half, and then rolled up in a tube. (No, we’re not doing anything on any kind of illegal chemical substance. :rolleyes: )

This has to be depicted as unrolling (think fruit roll-up) and then unfolding into the fully deployed position as a circular object with a hole in the middle. How would I go about doing this? Cloth simulation has many errors and I admit, is not my area of expertise. I have asked around and haven’t found any reliable answers, so I figured I’d just put this out there for general discussion, in the diminishing hope that I can find someone with an answer. I’ve practically exhausted all options, as far as I can think of them, and could use a new perspective! :o

This is the object that needs to be folded in half and then rolled up:

Rolled up like this:

The issues with using the cloth simulation is that there is so much interaction between the cloth faces, that it always fails. Also, there is the fact that the roll-up has the additional complication of being a semi-circular motion, meaning, the angle of rotation has to go around in a 180 degree fashion while it rolls up. I hope that makes sense… Imagine taking a coffee filter, folding it in half, and then rolling it up.

As you can see, it’s a bit complicated, which is why no one has an idea how to do it. I really could use some help.

Dan

Did you mean something like this:

roll-up.blend (561 KB)

I’ll leave you to sort the detail of the mesh.

Cheers, Clock.

Wow. Thank you for your excellent, prompt reply. That’s the closest I’ve ever seen someone get it! Very, very, nice! I never thought of the approach of using a curve modifier!

However…there is a bit of a problem. It’s a bit more complicated than that motion, and difficult to explain with just text. The motion involves three rods. Two of the rods are present along the center of the fold, so that the material, when it folds, folds over these two rods. A third rod is then placed on the outer edge of one side of the semi-circle. The two that are next to each other (with the cloth between them) must rotate around each other, simultaneously rotating along the Z-axis 180 degrees, and that’s how it rolls up.

Your technique is splendid. And is very refreshing after literally months of failed attempts. But my unfamiliarity with the curve modifier means I have to ask: can this technique be adapted to this new motion?

Screen shot of start position:

Dan

OK, leave it with me for the weekend, I’ll look at it for Monday

Cheers, Clock.

Dan

It’s going to be nearer the end of the week - events have rather overtaken me and I am up to my neck in work.

Cheers, Clock.

Perfectly understandable. I appreciate the help nonetheless.

Dan

Is this the correct motion of the rods?

roll-up.blend (588 KB)

If so I don’t quite see how the cloth can fold like this without creasing unless the rods are tapered, or the cloth rotates around the z axis with the rods. This latter option makes it possible by judicious use of parenting…:eyebrowlift:

Let me know and I will make some more progress.

Cheers, Clock.

The rods are tapered, smaller toward the center. Also, the two rods’ rotation is very close to what it would be otherwise, but also, they end up in the final position slightly rotated up to accommodate the cloth as it rolls into a slightly conical shape.

Hopefully that makes sense. Thank you so much for any assistance on this. Like I said, I’ve tried so many approaches to this, and nothing so far has worked.

Dan

OK leave it with me…

Cheers, Clock.

Sweet. Thank you very much.

Dan

Sorry - I am really struggling to get this to roll into a cone…

I am away for two weeks now, but wil try again when I get back.

Cheers, Clock.

It’s okay. I totally understand. It’s probably not going to be possible, because this is not the first time others have tackled this issue. Frankly, if you are able to do this, I’d probably say you’re far wiser than 99% of the rest of artists out there. This is a tough problem, and I’ve already told the client that this is probably not feasible in a 3D program.

Dan