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How do I animate a simple object based on a stroke in another layer?

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Reed Brown
How do I animate a simple object based on a stroke in another layer?
on Jul 25, 2017 at 5:20:13 am

Hi everyone,

Well, there's pleny of helpful info if I want to get a round ball orbiting a circle using a null layer, but the problem is I need my little red electron to orbit an elipse, not a round circle. I've created an oval stroke as it's own layer (drew it with the shape circle tool, turned off fill and set the stroke to 7px and blue). I also have the electron (red circle with gradient to give it some shine) on another layer. In the screen grab, I've positioned (not anchored) the electron ball over the stroke it's supposed to move over. Lovely.

There will eventually be a smaller second inner stroke/electron but obviously, create one, easy to create another. In the center of all this is a blue nulceus bunch I've already created in a pre-comp.

So how the heck do I get the electron ball to simply move along the blue oval stroke and loop 4-5 times?

I know this is something simple, but I just can't get it.

Please help! And thanks in advance!

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Liran Tabib
Re: How do I animate a simple object based on a stroke in another layer?
on Jul 25, 2017 at 1:18:22 pm
Last Edited By Liran Tabib on Jul 25, 2017 at 1:37:17 pm

Hi Reed

What you ask is pretty simple to do, copying the path data an pasting it to the position of the Electron layer.
But since this is with shape layers there are few things to check before copying and pasting:

1. Vector data must be copied from a bezier path so if you didn't create the Oval shape with the Pen tool you'd probably need to convert it, here's how:

Right Click on Content-> Ellipse 1-> Ellipse Path 1 and select the "Convert to Bezier Path" Command.
Now the Ellipse Path 1 changed to Path 1, so you can open it, select the Path Property and copy to the clipboard.

2. Now when you have the Vector data you need to paste it directly in the Position property of the Electron Layer.
So open the transform->Position property (or simply press P on the keyboard), Select the Position property and Paste.
now you can see that the Electron motion path is the same as the Oval Path. if it shifts a bit, you can move the Electron's Anchor point or adjusting the path by selecting all of the keyframes and dragging to motion path the the proper location.

3. Looping can be simply done by copying and pasting the keyframes 4 or 5 times, I personally Prefer to use the loopOut() or loopIn() Expression on the position value.

If you find your self doing this multiple times I suggest taking a look at ArrowHead. It's a tool I developed to create Arrows along paths But it's great also for attaching layers to the path and animating them along it.
You can find it in:

I hope this helps!

Best Regards

Liran Tabib

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Reed Brown
Re: How do I animate a simple object based on a stroke in another layer?
on Jul 25, 2017 at 9:27:21 pm

Hi Liran,
Thanks very much for your reply & instructions. Oddly, I wasn't able to locate anywhere the "Convert to Bezier Path" on the layer you iindicated and I'm on A/E 14.2 but who knows... Everything works 'till it doesn't. Anyway, I created the path in the pen tool in a shape, copied the path and all worked great. Copy/pasted groups of keyframes (didn't know you could copy start frame right on top of end frame for totally smooth movement), did a bit more work on the smaller orbit, changed colors, added text, arrows--and all worked great. Image below is the electron captured between dissolving from the inner orbit to the outer circle; orbits in sync with each other.
Again, thanks so much!

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