# How to make a bead shaped object pass through a string

I am trying to make this bead shaped object pass through a cylindrical helix. I have tried adding all kinds of colliders and tweaking their properties, both objects have a RigidBody, but the sphere just falls through the helix instead of passing(flowing) through it.Need Help!
I have posted a couple of images for your reference.
Thank You.

![alt text][2]

I presume you mean to have the bead pass over or around the unmoving helix so that it will follow a spiral path. (The helix is going through the bead.)

The physics engine isn’t good at dealing with problems where complex surfaces are in continuous contact. Even if you get it working, the parts will probably just rattle around and not get the smooth result you probably want. The physics engine is better at sparse scenes where convex objects occasionally collide with each other.

For this, it would be better to make sure the two parts don’t have physics collisions and just animate the bead’s position.

This is the formula for position over time t of a regular spiral up the Z axis:

``````x(t) = cos(t)
y(t) = sin(t)
z(t) = t
``````

Check it out:

You’ll have to multiply t by some factor and each line by some factor to get a perfect fit with your exact helix.

It might look something like this:

``````x(t) = cos(t) * ConeRate * t
y(t) = sin(t) * ConeRate * t
z(t) = t * StretchRate
``````

…where ConeRate is a value that affects how big the spirals get and StretchRate is a value that affects how tight the helix is along its axis.

both your meshes are concave, so you would need concave mesh colliders (untick the convex checkbox). But unity does not compute collisions between concave meshcolliders (as such collisions are costly).

The iTween method was bound to work perfectly.The capsule collider method worked perfectly. The animation method too worked perfectly! I added a trail renderer for a better visual effect. Thank you all for helping!