Spline Dynamics – Secure anchor points to prevent rotation

[Seun Jubril]

Dude, if you’ve figured out an answer to this, let me know. Dealing with the same issue right now.

[Jason Mettler]

It’s hard to tell by looking but it looks like your spline shape that is being swept is turned to the wrong axis. Try rotating 90 degrees on X axis

[Kyal Cundall]

So I found a solution and forgot about this post.

The “Hair Constraints” work well when the ‘hair spline’ uses a circle ‘sweep ‘. When you use a rectangle to sweep the ‘hair spline’, the rotation problem occurs.

There are a few things I have learned…

Ensure that you cache the dynamics, this creates a more accurate representation of the animation and requires less resources to run.

I also over came this by putting the entire earphone (both earbuds, cable and remote) into a null object (call it earphone null), the cable was straight linear and adaptive, i subdivided it to have 10 vertex points. I then applied a spline wrap to the earphone null (place the earphone null and spline wrap inside another null, call it spline wrap null). I created a hair spline with constraints and used it as the path for the spline wrap.

You need to ensure you have chosen the correct axis to align, switch mode to ‘keep length’ (to prevent stretching), play with the ‘From’ and ‘To’ settings to ensure the earbuds are not included in the spline dynamics.

Then place everything in another null call it “dynamic earphones”. You can then move that null around with a dynamic cable. If you need to move one of the earphones, ensure the constraint is attached to an object, make it invisible and animate that.

If you need more control over the animation, animate the align spline ‘offset value’, this makes the earphones follow a path you choose.

Below are some examples of what I have made using these methods:

https://www.youtube.com/watch?v=ZmTBzk9VLR4

https://www.youtube.com/watch?v=VvE5111I-gI

https://www.youtube.com/watch?v=kyGn0gtNZL0

I hope this was useful, it took me a while to figure it out.

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[Xavier Bonet]

Hi! I realise I’m a couple of years late… ???? but, for what it’s worth to anyone having similar issues, I was able to fix a similar situation using a different solve than that explained by the OP: I used the same spline as a rail.

Initially, I was using a Sweep and had a bumpy texture on my final object that would rotate unnaturally with every movement. I pinned the issue down to exactly what the OP has: the thing was banking like crazy, instead of acting as a “solid object”. That’s because it’s the spline that’s being affected by dynamics, and the spline is just that: a spline! a single string with no volume. I think there should be an option included into the Spline Dynamics tag that allows one to specify what the diameter or width, the volume, in any case, of the actual object to be rendered will be, because a spline by itself makes no sense. So the object “surrounding” the spline is just a shell that does what the spline does.

In my case, the splines generated hanging moss-like things, and these had to sway with the wind and movement; instead, they turned as if on a swivel. So what I did was change the Sweep for a Spline Wrap (because Sweep doesn’t have to option for a rail), changed the circle spline for a capsule, duplicated the spline in question, and set it as a rail in for the Spline Wrap! And although the result isn’t 100% what I needed, it’s about 95%, and that’s fine for this particular instance.

In conclusion, it does work, at lest for me, and it does stop the object from rotating on its axis. Still, I repeat I think would be better solved by including a specific command in Spline Dynamics.