# Baguette vs the Donuts OR Semi-Rigid Stick through Sleeve

Hi gang!

Seeing weird behavior with the physics engine. I’ve a flexible stick (as a series of joints, colliders, and hinges) I have a curved path of sorts, currently created as a series of toroids with simple mesh colliders.

Can be imagined as a small soft stick of bread pushing through a series of enlarged doughnuts, where the doughnuts are arranged so their centers form an arc. And where the bread straightens out if no collisions are acting upon it.

What I want to do is put the stick through the toroids prior to, or at, launch, but also maintain the stick’s ability to return to a straight form.

After many (many) failed attempts, how would one go about setting this up?

My first attempt, I positioned the stick within the toroids and ensured the spring angles of the joints were all set to 0 (so they would try to straighten out), however, apparently spring angle is calculated relative to the starting angle not the absolute angle of the joint, such the stick maintained it’s starting curve when no collisions acted up on it, instead of straightening out.

Re-positioning the stick on start brought me closer, but there was always the issue of the stick penetrating through the outer edge of the toroids (tweaked the bounce and penetration factors, but might need further tweaking if it will work at all)

Is there another technique to achieve on this? Basically just want a stick to appear to be going through a static sleeve. So perhaps even not using toroids, but something else?

Willing try to try just about any approach; I’m running out of ideas.

No one has tried similar?

It’s one of those things where I think there must be a solution I’m overlooking, as pre-placing jointed rigidbodies is something I would think comes up often with Physics.

Then again I could be wrong!

if it’s like a tank tread, that’s tough enough.

if it’s more like a crazy maze with user control, well…

that’s really tough and i think you’re going to have hard time getting an answer on the forums. if you can find someone on the irc, you might get a better talk thru. i know you’re not a noob but it could get pretty complex.

are you still on spring joints?

Joe: You can’t just adjust the zero point of each joint to zero through a script while the game is initializing?
Perhaps I am missing something…

I think I would use a mesh sleeve just because it sounds simpler, but I don’t know exactly how you have everything set up or what the requirements are.