# Sphere collision driven bending simulation

**URL:** <https://discourse.mcneel.com/t/sphere-collision-driven-bending-simulation/97804>\
**Category:** Kangaroo\
**Created:** [March 9, 2020, 4:12am UTC](https://discourse.mcneel.com/t/sphere-collision-driven-bending-simulation/97804 "2020-03-09T04:12:51Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![KristenLu](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/kristenlu/32/644006_2.png) [@KristenLu](https://discourse.mcneel.com/u/KristenLu)\
**Post date:** [March 9, 2020, 4:12am UTC](https://discourse.mcneel.com/t/sphere-collision-driven-bending-simulation/97804/1 "2020-03-09T04:12:51Z")

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Hi everyone,

I’m trying to simulate a specific bending phenomenon mentioned in this paper with kangaroo:

> **[Hydrogel Actuators as Responsive Instruments for Cheap Open Technology (HARICOT)](https://www.sciencedirect.com/science/article/pii/S235294071730197X)**
>
> Hydrogel actuators are a class of actuators that use the swelling of a hydrogel to achieve movement. The fabrication of such actuators is usually cumb…

There’s also a YouTube video showing the morphing process in you are interested:

[![](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/e/7/e/e7e36adce8c0c9c7b411e1e98403c9247818aab1.jpeg "HARICOT - cheap and easy fabrication of hydrogel actuators") ](https://www.youtube.com/watch?v=HWW-lTXcK2I)

As shown in the pictures below, a line of water beads were glued to the paper strip at the beginning, while the beads swelling underwater, the collision/squeezing between these spheres are causing the bending effect, and with different spacing between the beads, considering the time that takes for these beads start to reach each other, there would be different curvature results within the same time period; also as the time going on, the bending effect is getting more obvious.

 ![](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/9/6/9625aa0647f948d8010145fc668a8cd638945c34.jpeg)  
 ![](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/a/1/a190118e48cae5b87a1673f26ed38bd1d5e68bbd.jpeg)

And my goal here is trying to test this principle on some more complex shapes, here I had some promising physical experiment results with kirigami.

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/6/7/67f92bcfff153aa581c3f3256e73d3d0809a9e86.jpeg)  
 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/4/3/433ed975eca82fc60a8044633dbf0e4525d1a62a.jpeg)

something similar to these, but triggered by water beads instead of a pulling/hinge power

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/9/7/97c16d2f53b975bccd17c83fb516c39dc61b19c9.jpeg)

I did some search work on this topic and found some relevant simulation:

[![](https://i.vimeocdn.com/video/624096769-8940724577340d44dbac77c31c6cf70dd5da741d91f8cb503fe44f6ac85b5a14-d?f=webp "Plastic deformation") ](https://vimeo.com/208708625)

> [@Kangaroo bend](https://discourse.mcneel.com/t/kangaroo-bend/80842):
>
> Does anyone know how to do this!?

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/3/2/32d1771be18805f1de43240803eb556a9bb4d4c5.png)

> **[trouble bending a flat module so that it becomes tridimensional](https://www.grasshopper3d.com/forum/topics/trouble-bending-a-flat-module-so-that-it-becomes-tridimensional?groupUrl=kangaroo&)**
>
> Hey all,
> 
> I want to get from a flat shape to something like in the above pic.
> I attached simplified definition of my approach so that someone can take a loo…

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/f/5/f5faef7a389a320e9ca441e0123caa4dda84d3db.png)

> **[Getting Control over the Bending Process](https://www.grasshopper3d.com/group/kangaroo/forum/topics/getting-control-over-the-bending-process)**
>
> Hi all, I would like to be able to bend polylines using Kangaroo the way they did bend wood in the pre-computer era to build ships. Like so:
> I found a definiti…

post by @DanielPiker  
For the beads part, although this is a simplified 2d model, this is the most close one I could found, however I had bad luck applying my pattern on it, the outcome just went zig-zag.

The main confusion here is how to set the anchor points, as they are free of moving underwater;  
Another thing is that I’m not sure if the anchor point should be idealized as a single point(as in the 2d spline model) or actually a group of points regarding the way the glue was applied. I’ve also looked at this discussion below, where @DanielPiker post a resolution for open-open mesh and close-close mesh “intersection”, I’ve played with them happily, but for what I’m going to achieve here I’d suppose it to be a close-open (sphere swelling/strip ignoring thickness) combination, and with that the applied, the outcome just went like explosion.

> [@Mesh kisses](https://discourse.mcneel.com/t/mesh-kisses/78823/37):
>
> [StickyKisses.gh](https://discourse.mcneel.com/uploads/short-url/Acq0MVeBQHnUQKd56EBXmRDcBhG.gh) (54.3 KB) Here a goal that pulls the points of one mesh onto another, so they stick together when they kiss. It also includes a ‘chaperone’ force to prevent the meshes from penetrating each other.

I’m still not sure if it could be simplified to a 2d model just for circle packing and curve bending, because eventually I want to apply it to a kirigami simulation which forms a 3d shape.

I would be super grateful if anyone has any thoughts on how to build up this simulation, whether on a single strip or for a designed pattern.

Thanks!  
Kristen

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**Author:** ![Mahdiyar](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/mahdiyar/32/472862_2.png) [@Mahdiyar](https://discourse.mcneel.com/u/Mahdiyar)\
**Post date:** [March 9, 2020, 6:32am UTC](https://discourse.mcneel.com/t/sphere-collision-driven-bending-simulation/97804/2 "2020-03-09T06:32:03Z")

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![SphereBending](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/6/0/60208cc8624fc11e68e2958e0fd1f58b99f6ff35.gif)  
 ![SphereBending](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/e/9/e92708629c746c61c5b9418077dec72ca353bfed.png)  
[SphereBending.gh](https://discourse.mcneel.com/uploads/short-url/3ipFRjagcc7mjJBY18DSseHQtE.gh) (26.8 KB)

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**Author:** ![Mahdiyar](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/mahdiyar/32/472862_2.png) [@Mahdiyar](https://discourse.mcneel.com/u/Mahdiyar)\
**Post date:** [March 9, 2020, 7:22am UTC](https://discourse.mcneel.com/t/sphere-collision-driven-bending-simulation/97804/3 "2020-03-09T07:22:14Z")

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[https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/8/5/85b5507e178e29863482c8413bd95dcf334c36ac.mp4](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/8/5/85b5507e178e29863482c8413bd95dcf334c36ac.mp4)
  
[SphereBendingMultiRad.gh](https://discourse.mcneel.com/uploads/short-url/bvVXs2uGgk4W3IrjGlBcDWrztZ.gh) (28.4 KB)

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<div class="post-metadata">

**Author:** ![KristenLu](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/kristenlu/32/644006_2.png) [@KristenLu](https://discourse.mcneel.com/u/KristenLu)\
**Post date:** [March 9, 2020, 2:58pm UTC](https://discourse.mcneel.com/t/sphere-collision-driven-bending-simulation/97804/4 "2020-03-09T14:58:51Z")

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Thank you so much for your help, your scripts simulate exactly what I’m working on!!! 🤩