Noob Question: Move a layer in the opposite direction of a different animated layer

[Guest]

So say that I have an icon that I animate on the Y-axis +40px, but instead of trying to hand key the other layer each time, is there an expression I can write to have the other layer move in the opposite Y direction the same amount of units (ex: -40px)?

Thanks!

[Dan Ebberts · Accepted solution]

You have to define what the y movement is relative to. For example, if you want one layer to mirror another layer's y movement since the first frame, you could do it like this:

p = thisComp.layer("leader").transform.position;

value + [0,p.valueAtTime(0)[1] - p[1]]

If you want to mirror it around a particular reference y value, it would be like this:

yRef = 540;

p = thisComp.layer("leader").transform.position;

value + [0,yRef - p[1]]

There are other variations/interpretations--it depends on what you're after exactly.

Dan

[RyanD7]

Hi Dan,
Thanks for this, worked a dream.
However I hoped you could help with an addition to this. This currently works to move my y value in the opposite direction, but how can I add to this to move the x value in the same direction? I tried duplicating and changing y to x but to no effect.

Thanks,
Ryan

[Dan Ebberts]

If you're talking about the first version, this should work:

p = thisComp.layer("leader").transform.position;

p0 = p.valueAtTime(0);

d = p - p0;

value + [d[0],-d[1]]

Dan

[RyanD7]

Sorry Dan my bad, I'm using the second version;

yRef = 640;

p = thisComp.layer("Left Face Null").transform.position;

value + [0,yRef - p[1]]

I just need to add something to this which would also move x but in the same direction, not the opposite.

Thanks,
Ryan

[Dan Ebberts]

Something like this, I guess, but you'll need to adjust the value of xRef:

yRef = 640;

xRef = 640;

p = thisComp.layer("Left Face Null").transform.position;

value + [p[0] - xRef,yRef - p[1]]

Dan

[Micha25187607ueks]

Hey! I know this is many years down the line, but how would you go about mirroring just the x value here?

[Dan Ebberts]

Something like this, probably:

xRef = 640;
p = thisComp.layer("Left Face Null").transform.position;
value - [p[0] - xRef,0]

[Micha25187607ueks]

Hi,

thanks for getting back! In my case, I have a circle moving from right to
left. I want another circle to start from the same position, except move in
the opposite direction (left to right). It's a bit difficult because I
spent quite a lot of time animating the circle moving right to left (using
easy ease) and simply want to replicate the velocity of that movement, just
right to left.

[Micha25187607ueks]

Thanks for getting back! In my case, I have a circle moving from right to left. I want another circle to start from the same position, except moving the opposite direction (left to right). I spent quite a bit of time animating the circle moving right to left (easy ease mostly) and simply want to replicate the velocity of that movement, just right to left.

[Dan Ebberts]

Maybe like this:

p = thisComp.layer("right to left circle").transform.position;
x = p.key(1).value[0] - (p[0] - p.key(1).value[0]);
[x,value[1]]

[Micha25187607ueks]

Yes, that worked! Only issue is they both have the same starting position
now. Is there any way I can offset the "left to right" circle's starting
point?

[Dan Ebberts]

Like this maybe:

p = thisComp.layer("right to left circle").transform.position;
x = (p[0] - p.key(1).value[0]);
value - [x,0]

[Micha25187607ueks]

Perfect, thank you!

How would you go about reversing the exact motion on the same object a few moments later. For example, the circle enters the frame from right to left with a certain velocity - how do I replicate the exact same velocity on the same object, as the circle exits frame from left to right

[Dan Ebberts]

Something like this probably:

delay = .5; // pause before reverse
if (numKeys > 1 && time > (key(numKeys).time + delay)){
   valueAtTime(key(numKeys).time - (time - (key(numKeys).time + delay)));
}else
  value

[Micha25187607ueks]

Working perfectly now - thank you!

For some reason, when I alter the daley = .2 it does not shorten the time before reverse?

[Dan Ebberts]

delay = .2;

shortens the delay for me, as I would expect.

[Micha25187607ueks]

Does this look correct?

[Dan Ebberts]

It does.

[Micha25187607ueks]

I hada a stray keyframe messing things up. All good now. Deeply thankful for the help, Dan. All the best!

[Micha25187607ueks]

My last rookie question - I should've done this before animating, but how would you go about centering these two shapes within the composition? The align tool just forces the both of them ontop of each other in the middle.

[Dan Ebberts]

Hopefully, someone else will jump in, because I'm not sure what you're asking...