AE Expert need : Following a motion path without changing positions

[LordVal]

Hi dudes,

A lot of thanks for the AE experts who will answering to me.

It's a problem that I never read a solution on anywhere.

So let me explain, I have a lot of objects going out an optical fiber.
All this object have a mandatory starting and ending position.
Instead of animate all theses objects one by one, I wish set them to follow a predefined curved path without changing starting and ending postion, they just need to follow the curve.

How i can do this?

Thanks again.
Val

[Mike_Abbott · Accepted solution]

Here's a suggestion:

Animate the position of your first layer - it just needs 2 keyframes. Use the Bezier handles to shape the motion path to match your curve. Now also apply this expression to the same layer's position property - adjusting the 'delay' value as you require:

delay = 10; //number of frames to delay
d = delay*thisComp.frameDuration*(index - 1);
thisComp.layer(1).position.valueAtTime(time - d)

Now add all your additional object layers directly underneath this one.

Highlight the position property of your first layer - the one you've just put the expression on - then go:  Edit menu > Copy Expression only. Select all your other object layers and paste. This will copy the same expression to those layers.

All layers should now follow the same path with a 10 frame delay.