opacity to multiple layers

[Andy George]

This would be a good job for expressions.

You can use the quickwhip to link the opacity of one layer to another for an expression that would look something like this:
thisComp.layer(“Red Solid 2”).transform.opacity

Then copy this expression (edit-copy expression only) and paste it onto as many additional layers as you like.

An easier to control method might be to add the Slider effect to a layer and then quickwhip your opacity to the slider for an expression that would look more like this:

thisComp.layer(“Red Solid 3”).effect(“Slider Control”)(“Slider”)

These websites does a good job of explaining how expressions work
https://www.jjgifford.com/expressions/basics/index.html (more basic)
https://www.motionscript.com/

-Andy George
Senior Editor
http://www.chiselindustries.com

[Sabah Shahdi]

Hi dear.

I imported an illustrator world map to after effect which is in layers (each country has a layer).

I’m trying to make a world map that will be scanned from left to right.
a simple solid layer will make scanning process.

the question is that how link opacity of each layer to position of that solid?
when that solid crosses over a layer, opacity of that layer change to maximum value and in other cases opacity change to minimum value.

I think it is possible to link the opacity of a layer to position of another layer, but how?