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Vellum semi rigid Helix type hose


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Hi Everyone

I am undertaking a simple industrial robot arm type machine which has a nylon spring hose.

I am doing the hose with a little Vellum SOP set up, which is, I think the right tool for this effect?

Unexpectedly, the hose desparately sag and melt no matter how much stiffness, substeps, iterations etc.. I have tried different constraints model Struts, Pressure..

Ideally it should stay firm and wiggle/swing a bit as I animate the arm.


Would anyone check my scene quickly, pretty sure it's a simple mistake of mine but I am not so experienced.




Many thanks






Edited by Vinz
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Hi Vincent !

I think your issue is because you are trying to simulate the whole wire geometry
Keeping it as a polyline will be both faster and work better for what you want

Here's my take on it using your file (sorry for the absolute chonker of a gif, a few minutes long)


I am aware this is not a sexy spring, but I guess it kinda works. I'm by no means a Vellum expert, but I hope that's at least a good start for you !

The key is to have enough Substeps. And if you want self-collisions, prepare for a slower feedback. I recommend setting it all up without collisions, and turning them on at the end when quality is required.

Hope that helps !


Edited by Alain2131
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Here's another (arguably too long) gif, just for funsies


Adding an outer shell for the spring to collide against, and exaggerating the animation to force interpenetration of the spring with itself at the bottom to see how vellum handles that
The answer - surprisingly well ! (with enough constraint and collision iteration) This is stable and not exploding in any way. Noice

By the way, this simulated at 1.8fps, so it took 2m20s for the 240 frames at this quality.

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Oh, Man..  I had a bit of a lonely moment thinking my stuff was not raising much interest

This is fantastic!

In the meantime I could just have the spring at least holding itself by swapping the' pin to target to 'attach to geometry' instead.. but I had absolutely no flexibility.. the least little force and the mesh would rip apart all that with silly cooking time.


So I am going to dive straight into your scene and  get back to you soon with the news.


Also I would be interested to know how you managed to stuff as much screen time playing live at a nice resolution directly on here


Thank you again  speak soon

Edited by Vinz
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Hi Alain

I have the great pleasure to tell you that this is working beyond dreams

I changed very few things, only the pinning of each ends of the curve; the dynamics were set absolutely right for this type of material.

Cooking time is almost insignificant and the animation plays back at 12fps with the polywire


This setup would even handle a lot more stress than shown here.


I am thinking of doing a spray paint nozzle and have this thing paint stuff or write.. I am still considering the best approach.. attribute transfer, Pyro spread temp attr..

If you wish to join this little project, you are more than welcome


Many Thanks



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Hey Vinz !

Awesome ! Glad it works well

One thing I would recommend is lowering the amount of points in the second resample.. I put it at 1200 points (which was your original amount), but that is a bit intense just for visual feedback. You can easily halve it with basically no visual impact, which resulted in 23-24fps playback on my side with 600 points. Even 300 points might be good enough.
You might even be able to consider lowering the amount of points being simulated if you don't need that much precision.

Although I do appreciate the offer, I decline.

Also, the software I used for the gif is ScreenToGif
It's pretty light and works well for my needs, and saving the gif using the Octree Encoder yields good result


Edited by Alain2131
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