Animated spline with wave motion


#1

Hi, I’m trying to animate a curve (spline) with wave motion in a 2D plane (XY axis). Simple right?

To animate the curve I rigged it with nulls at the vertices, and animating the nulls on the XY axis. The wave motion is via Mospline from a Formula effector. When I move the nulls (vertices) of the spline in the plane, the spline rotates for some reason. Because the nulls are moving in a planar manner/positionally, I have no idea why the spline is rotating.

Maybe someone knows how to lock the spline on the XY axis to prevent rotation? Maybe my spline settings should be changed? Maybe Ishould rig everything in a different manner? Open to any suggestions.

It seems like a very straightforward animation but I’m running into some odd issues. Attached file shows the problem.

Thanks!

curved wave_animation_01.c4d (298.3 KB)


#2

I’m a bit confused about your problem and your set-up.

Is your problem referring to the flickering of the joint/spline, when I hit play on your file?

If so, have you tried reworking joints. Have the number of joints equal with the number of spline points .
Currently, there is 4 spline points but only 2 joints.


#3

Hi bentraje, thanks for replying to this post. The spline animation/joints are set up using this method starting at4:00 to give spline control.

Maybe you know a different method that allows for position,scale, rotation control at the vertex level? I’d like to know if there is a better way and allows the spline/vertex control.

The problem is when you hit play on the animation, the spline ‘flips’ (or flickers) . I don’t want it to flip, I want it to stay in the XY plane without flipping. Theoretically the spline should not flip, as the motion from the vertices is all in the XY plane without any Z motion. It should be moving smoothly.

I’ve found the problem is in the sweep (or at least I think that’s where it is), it’s rotating when the spline is animated. From what I’ve seen, I need to duplicate the spline and offset it and use it as a rail. I’m not sure if this will work with an animated spline but it works with static splines. I’m guessing I need to offset it in the Y, which will make things really difficult, as the animations for each spline will be different.

If anyone knows a good way to do this, or if this is the wrong direction, your help would be greatly appreciated.

Thanks!


#4

Hey @plasticbag05,

I’d recommend two things:

  1. The flickering/jumping of the Spline definitely has something to do with the time in the formula effector.
    You’re on 30fps, so if you go to Frame 30 and press G (or frame forward) you’ll see the Spine jump.
    Now - set your global fps to 25 and try again. Jumping will occur at Frame 25->26.
    Maybe you wanna get rid of the time in the effector?

  2. With a little bit of xpresso, you can easily set up a spline that is tied to Nulls without using joints. I’m pretty sure that you won’t have any jumping/flickering of the spline.
    If you use a cloner cloning Nulls and connect those Nulls, you can also extend the spline (its length) super quick.

Let me know if you need any help with that xpresso stuff…


#5

Hi Gregor,

Thanks so much for the help!

I’m impressed of the way you found the flicker tied to frame rate/time. I’m not sure if the formula will work without a time variable, as it’s part of the sine wave equation. Maybe time (t) isn’t needed?

If you can, I’d like to see your technique using Cloner/Nulls/Xpresso for animating a spline. From the small amount of Xpresso I really like it and would like to see how you set up and control a spline with it. If you have a demo file you can post for me to see, that’d be great. Or point me in a direction, any help is appreciated!

Thanks!!!