I’m working on a mechanical iris.

What I want is a sort of rubber sleave/cover over the leaves of the mechanical iris so you can’t see the leaves.

enter image description here

I’m using a cloth simulation to get the mesh reacting on the leaves of the mechanical iris. Problem is that I can’t figure out the right setting for the cloth simulation, it doesn’t work properly in any option I tried.

• All the leaves are collisions

• On the sleave mesh I applied a cloth physic with this settings


enter image description here

Is there somebody who knows how to fix this problem or knows a other method do achieve the same result?

  • $\begingroup$ How this thing should look like? So i.stack.imgur.com/YGhy9.gif ? $\endgroup$
    – Blunder
    Jul 29, 2021 at 17:57
  • $\begingroup$ Yes kinda like that, how did you achieve that? $\endgroup$
    – Renst
    Jul 30, 2021 at 10:47
  • $\begingroup$ I've increased the Shrink value a little bit and used the Rubber preset for the cloth physics $\endgroup$
    – Blunder
    Aug 5, 2021 at 17:40
  • $\begingroup$ Thanks for your reaction. Can you explane it al littlebit more? I dont know exactly what you mean with the Shrink value. And how you make to gape close and open $\endgroup$
    – Renst
    Aug 16, 2021 at 15:01
  • $\begingroup$ It's in the Cloth simulation settings, where you can use the Shape > Shrinking Factor value (+/-) to tighten or widen the cloth. The cloth settings of the Rubber preset do make the gape close and open but when I've modeled the mechanics as you did I had to give it a little Shrink Factor. Maybe my cloth mesh was bad? $\endgroup$
    – Blunder
    Aug 19, 2021 at 1:36

1 Answer 1


Here is a lazily modeled mockup because I can no longer find my first detailed model. It's a disc with Collision physics and a Shapekey that reduces the hole in the center. A torus with a Cloth physics overlaps it. There is a short animation that switches between the shape keys.

I've turned off Gravity, and increased the Shape > Shrinking Factor a little (it's not needed for this model but for the first one). Here is the initial state: open state

Then used the Rubber preset for the Cloth settings and ran the animation. (The presets are in the "hamburger menu" right next to the Cloth section.) And I've given the Cloth settings some Pressure to dampen the torus a bit and make it wobble less when the "iris" opens again. closed state

Here's a test with the previous detailed model. It looked like as shown above in the question's first screenshot. The open/close mechanic made the cloth spin around. closed state


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