I have a buoy on the surface of a fluid simulation that moves around. It has no Rigidbody attached, only a few rotation and location constraints which should cause no problem.

I am wanting to create a rope that attaches to the floor of my simulation and the buoy. It should fold relatively naturally as the line slacks. I have attempted one tutorial which got me close, creating a rope that bends and is affected by gravity, but it breaks if I try to attach the end to the buoy. (Link Below)


I have tried hooking a bezier curve but it didn't want to attach to the vertice. (The little icon said I couldn't :( )

If anyone has any tutorials or ideas, it would be great if you could post them.

I have a relatively good knowledge of blender though I am a bit vague on where to find buttons and such :)

If any additional information is required I will help where I can.


Apologies, but i am on a school laptop and websites like imagur.com are blocked, so no images :( FYI, i wont see yours either, sorry ;P

My fluid simulation is basic, restricted by the domain and a starting fluid object and some small waves.

I have a small plain subdivided with shrinkwrap on it wrapping to the fluid domain, so it 'follows' the surface

I then have a buoy that is constrained to that small plain by z axis and all rotations so it seems to "float" on the surface

I have another Plane on the floor with a passive rigidbody and collider

Now the string (this is what i did):

I had a single edge, one vertex at the buoy, another on the floor. I then subdivided it 30X. I then saved each end point separately to a vertex group. I then hooked the vertices to the floor and buoy (I also tried empties). I added the softbody simulation and followed the steps in the link (maxing default and stiffness). The rope held place but only the first vertex moved when the buoy moved. I then tried disabling goal, getting a realistic rope effect, with no edge stretching as should be, but both end vertices would not stay hooked. Im stumped, but this is the closest I have gotten. I don't have any add ons if that makes a difference. If you want to know any preferences or settings of blender or solo objects, just ask :)

  • $\begingroup$ Does it have to be rigid body? While it can be done with rigid body constraints and then hooking a curve along the chain of rigid body objects, it’s probably simpler to achieve using Soft Body. See blender.stackexchange.com/a/98438/29586 $\endgroup$ Jul 24 '18 at 13:02
  • $\begingroup$ Related blender.stackexchange.com/questions/100642/… $\endgroup$ Jul 24 '18 at 18:38
  • $\begingroup$ Thank you Rich, I had never thought of this, I will give it a shot and see how it goes, and yes I do require the rigidbody as it must not fall through the floor, but it should be little problem with what you suggested. $\endgroup$ Jul 24 '18 at 22:42
  • $\begingroup$ Thankyou Rich, this is the closest I have gotten, but the rope i have made falls withought being pinned to the empty. It stays when I use goal, but it doesnt move like i want it to. I have constructed it as multiple verticies in a line and it works great as a rope but i just can't seem to get the end vertice to attach. Any ideas? $\endgroup$ Jul 25 '18 at 2:27
  • $\begingroup$ @BigfootBlondy without seein your SB settings it's difficult to tell. Yoo need to use the goal pin setting (using a vertex group that just has those hooked vertices) to pin the hooked vertices in place and set the goal strength and stiffness so those SB vertices stick to the hook. If you can share some details of your setup I should be able to help. $\endgroup$ Jul 25 '18 at 12:40

Many thanks to Rich for helping me solve this!

I created a single edge at the length I wanted my string/rope. I then subdivided it till I saw fit (will not look choppy).

Create three vertex groups: One for one end, one for another, and one with both (in my case pin_Float, pin_Floor and pin_Ends)

In turn, click on each control object and hook to the specified ends (not the double ended one ;) )

Add a soft body to your string and set 'default' and 'stiffness' under the 'Soft Body Goal' to max. Then underneath assign the vertex group with both ends to 'Vertex Group'

Play and adjust the settings under 'Soft Body Edges' until the rope moves as required

I also applied 'Soft Body Self Collision' and a Skin modifier

The Rigidbody and Collision physics can also be applied making it very easy to use.

Again, thanks to @Rich Sedman for his help.

  • 1
    $\begingroup$ What does this answer provide, which isn't found in the original answer? Currently, I don't see the difference. $\endgroup$
    – Leander
    Jul 26 '18 at 8:38
  • $\begingroup$ I missed the part to select the vertex group in the soft body goal settings. mostly a minor error by me. I was just repeating the process in detail for anyone having the same issue I did :) $\endgroup$ Jul 28 '18 at 1:56

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