In After Effects how can I generate the value of an opposite x position and then send that value to an effect on another layer?

Question

e.g.

my composition width is 4480

I have a layer with a gradient ramp effect with an x start positon of 1026 and I want to generate and store the value of the x position on the other side of the composition which would be 3454.

Then have a duplicate of that effect on another layer get the stored value or have the value sent to it

Answer 1

I think what you're asking to do is simple using Expressions. If you alt-click on the stop watch of any keyframe-able control you can write an expression to connect that control to another control. So if you want to control the end of ramp's x position using the start of ramp's x position in your example, it would be:

x = 4480-(effect("Gradient Ramp")("Start of Ramp")[0]);
y = 1080;
[x,y];

The [0] indicates an array - it means "take the x position of the "start of ramp", which has two values, x and y, which can be called as [0] or 2 in the array.

To duplicate this in another layer, duplicate your first layer using cmd+D, then add an Expression to the start of ramp in the duplicated layer:

You can use the pickwhip to select the control you want to enter into the expression