View Full Version : Bullet Dynamics - Cable/Rope question

09-01-2016, 09:48 AM
Hi all,

I'm working on a little test scene where I have a rope/cable controlled with Bullet constraints (via bones) and have ran into a problem.

The cable needs to be attached to moving objects at both ends, the 'origin' end of the cable is no problem, but I was wondering if anyone knew how to connect the far end of the cable to another object?

I know there are other methods of creating said effect/rig using a polychain etc. but wanted to see if it would work with Bullet.

I'm a little stumped with this so any help would be most apprectiated.


09-01-2016, 10:17 AM
Can you not just simply parent the other object to the last bone in the bullet setup?
or use some of the newer hinges options?

Eh..I was too fast maybe, you said both objects are moving, well..I would guess use hinges in 2015.

otherwise I would as you also mentioned, use a polychain, and that doesnīt exclude bullet in no way, you simple make a polychain and make it deformable bullet object, and make sure the other objects are covering the ends of the chain, what you do then is to metalink a cable mesh to fit the polychain, not sure which type of body you would use for the ends though, so that may vary, kinematic or parts, or rigid?

so step by step, what is the type of object in the beginning and end, what type of motion, and what type of bullet mode are you putting on them?

09-01-2016, 10:47 AM
Thanks for the quick reply. :)

Basically I've built a very simple robotic arm (just testing/learning all the bullet stuff) so I'm trying to get cables between all the different parts of the arm. At the moment I'm using Point to Point constraints. I've got the cable 'swinging' between the first and last bone (both kinematic) and the 'root' end of the cable attached to the 'upper arm' object, I just need to figure out a way to connect the 'end' bone to the 'forearm' part of the robotic arm.

09-01-2016, 12:01 PM
Just a thought: maybe you could set up the bone chain to branch out from the middle of the rope, so that the ik could point to both moving objects?

I'm not sure if this is relevant to your setup but a couple of years ago, I had to animate a scene where a large banner was being towed by aircraft. I used Bullet Bone Dynamics in a beta version where I worked at the time, and I remember I had some issues with parenting the towed object.

From what I recall, I had to:

1. scan the bullet 'rope' using SoftFX.
2. used EditFX to pick a point in the rope where the object could be 'attached'. (The point number will appear in the viewport.)
3. then select Make Path from under the Commands drop down. This will generate a null that has the animation from the point.

Once I had the animated null, I could parent the banner to it. This also allowed me to calculate Bullet cloth dynamics to the banner in a separate pass.

I'm not sure I did the above because I couldn't do both types of sims at the same time, and I haven't tried this in the current 2015.3 release, but maybe the 'EditFX' part will give you some ideas?

09-01-2016, 12:09 PM
Sorry, I wrote the above before I saw your last post.

There was a Worley plugin designed specifically for what I think you're describing. I think it was called Hoser? It's been many years since I used it but it was really easy to use. From what I recall, it didn't use bones, just a few nulls to indicate where to attach the ends of the rope/cables/hose and maybe a control null in the middle...something like that anyway. I'm not sure the plugin is still available or if it even works with 2015. (I'll check on that at home tonight.) I think the plugin did at least get an update for x64.

09-06-2016, 01:47 PM
I think bullet bone dynamics may work too, might not be ideal since you need a lot of bones perhaps, but making sure the bones are created in right order then make point to point dynamic object of them when they all are selected, this will make them dynamic, meaning each bone will by a rigid body, and each connection between bones are automaticly created as a hinge type (point to point) you could also vary with standard hinge.
once the bullet bones are created, the first bone is kinematic, you could make the last bone also kinematic, or reduce itīs weight, so when this bullet bone dynamics are connected to pieces, it should work a bit like a rope.