Move one layer in opposite direction (in Y axis) of another layer

[Andrei Popa]

I cant really re-create your situation to test this, but here is how i think you can solve it. Put this in the back layer’s position

pos = thisComp.layer("Your fron layer").transform.position; //this is the front layer's position
startPos = pos.valueAtTime(0); //here you must put a time value that is before the wiggle.
yDiff = startPos - pos;
value + [0,yDiff,0];

Andrei
My Envato portfolio.

[Kevin Dearing]

Thanks Andrei, that’s basically what I’ve been trying to do but you really helped me with the object model a good bit. One thing I neglected to mention is a small (but important issue).. The front target’s position is: [720, 540, 0]
And the back of the target is: [648, 316, 1]

So there’s a delta of: [72, 224, 1]

So, now I have it so that the front (which is actually the “back” of the target) is bouncing with the wiggle, and the back (what I’m trying to apply the expression on to match the bouncing) is staying exactly where it started out.

The first expression below is giving me that… (Note, I decided that I want z to stay at 1 no matter what so…)

So, what I’m thinking is that I need to get the movement that the wiggle is introducing maybe by using ~.position.valueAtTime(time) – ~.position.valueAtTime(time -1) and adding that to my “front” layer..

I’ve tried a number of ways but I seem to be screwing that up! Maybe just brain dead at this point!

backOGPos=thisComp.layer("Tgt_Back").transform.position.valueAtTime(0);;
frontOGPos =thisComp.layer("Tgt_Front").transform.position.valueAtTime(0);

xDiff = backOGPos[0] - frontOGPos[0];
yDiff = backOGPos[1] - frontOGPos[1];
zDiff = backOGPos[2] - frontOGPos[2];

prevBkPos=thisComp.layer("Tgt_Back").transform.position.valueAtTime(time -1);
curBkPos=thisComp.layer("Tgt_Back").transform.position;

xDelta = prevBkPos[0] - curBkPos[0];
yDelta = prevBkPos[1] - curBkPos[1];
zDelta = prevBkPos[2] - curBkPos[2];

x = curBkPos[0] - xDiff + xDelta;
y= curBkPos[1] - yDiff + yDelta;
value = [x, y, 1];

[Andrei Popa]

That is so overcomplicated…
Here is an expression if you want the x to modify same as front and y to the opposite(I thought you only wanted to move the y position from your initial post); In this expression, the “Tgt_Back” is the layer with the wiggle(i am guessing this one has the [720, 540, 0] values) and the “Tgt_Front” is the one that has inverted y. This is applied to “Tgt_Front” position.

initialPos = [720, 540, 0];
wigglePos = thisComp.layer("Tgt_Back").transform.position;
difference =[wigglePos[0]-initialPos[0], initialPos[1]-wigglePos[1],0] ;

value+difference

The idea is this. Value gives you the value of this property before the expression. So you only need to get the difference between the wiggle value and the initial position of the wiggle layer. And just add that to your value. If you want the same direction, you subtract the initial position from the wiggle. If you want different directions, you subtract the other way around(the third row in the expression).

I’m just trying to make you also understand how this work, not just use it.

The last row is something like [648, 316, 1] + [xRandomWiggle, -yRandomWiggle,0].

Andrei
My Envato portfolio.

[Kevin Dearing]

Thanks again for your time… I do tend to over complicate things from time to time.. And thank you for helping me to understand but it’s not working.. Here’s a small render of the issue I’m seeing with the below code…

https://youtu.be/oRaDdXv4r4o

initialPos = [720, 540, 0];
wigglePos = thisComp.layer("Tgt_Back").transform.position;
difference =[wigglePos[0]-initialPos[0], initialPos[1]-wigglePos[1],0] ;

value-difference

[Andrei Popa]

I am just trying to understand your project now. So you have 2 layers. The face layer and the back layer(face of cards and back of cards).
You have a wiggle on one of them.

1.Which one has the wiggle?
2.Is your wiggle applied only to y position?
3.How does the second layer relate to this wiggle? Are they parented? Or is it just through my expression?

The way I think this should work is you take the main layer initial position. You calculate the difference created by the wiggle expression and then you add or subtract that difference, depending if you want it to move the same direction or contrary.

Andrei
My Envato portfolio.

[Kevin Dearing]

Hi again. No, the comp with the target has a layer for the front, a layer for the back and a couple other layers. The front and the back have track mattes to create the holes. This comp is a layer in another comp, the main one. That is where the wiggle is, on the pre comp layer.

Originally I had the front and back parented thinking that would cover the wiggle but they were moving in opposite directions even then.

I had the wiggle on x y and z but the main concern is y.

[Kevin Dearing]

I think the problem is that the back layer (with the face cards) had to be rotated on the y axis, 180 degrees (but like I mentioned before I used a flip effect) otherwise when the camera (in the main comp) came around it would be inverted. I am thinking when I get home I’ll invert the image in photoshop shed replace it, remove the flip and hope that the wiggle moves everything the same way after that.

[Kevin Dearing]

Well, that didn’t solve the problem.. The wiggle on the precomp layer is still moving the 2 layers inside the precomp in different directions.. Strange..

[Kevin Dearing]

Well I feel really stupid. I had the target precomp in my main comp twice.

Removing the duplicate and setting things back to normal (where in the precomp all of the layers were parented together) worked perfectly.. No expression was needed afterall (other than of course the wiggle that I put on there which was, in fact, working correctly)