[Filip Vandueren]

They can’t, but expressions also can’t control if a layer is active.
No more than they can change the layer order, the label color, the quality setting,…

Expressions are by definition only applied to keyframe-able properties.

Why would you need an expression to shy a layer, it has no effect on the render?

Scripting can set the .shy property of a layer without a problem though.

[Filip Vandueren]

You can use just 1 slider, but every propery you want to control needs its own expression.
An expression can not set another property’s value.

In your example it could be as simple as:

Blur Radius:
thisComp.layer(“Controller”).effect(“Slider Control”)(“Slider”);

Opacity:
if (thisComp.layer(“Controller”).effect(“Slider Control”)(“Slider”).value < = 0) 0;
else 100;

Layer 2’s blur:
thisComp.layer(“Layer 1”).effect(“Fast Box Blur”)(“Blur Radius”)+50;

[Filip Vandueren]

The simplest way is to convert it to a path and animate the path shape.
Rectangle shapes are always drawn from their center so you need to animate both size and position to give the illusion of scaling from a corner.

[Filip Vandueren]

This is an excellent introduction to expressions:
Animoplex

https://www.youtube.com/watch?v=SFgWa5G0VAE&list=PLvr5U5ZSt6IzHyvSL9fo0M9NRPsTvra31

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[Filip Vandueren]

This is simply achieved by not animating position but anchorPoint instead.

[Filip Vandueren]

you can take some samples at different times and average them out, that is how smooth() works.
so something like.


L=thisComp.layer("text_iso");

r=[0,0];

for (t=0; t < 0.5; t+=0.05) {
s=L.sourceRectAtTime(time+t);
r+= [s.left + s.width/2, s.top + s.height/2];
}
r/10;


[Filip Vandueren]

the sourceRect gives just the dimensions of the source, so yo have to take into account rotation, scale, parenting,…

top left would be this:


l=thisComp.layer("Text");
sr=l.sourceRectAtTime();

pos = l.toWorld([sr.left, sr.top]);

if (thisLayer.hasParent) parent.fromWorld(pos);
else pos


[Filip Vandueren]

This expression for your expression-selector:


txt=text.sourceText.value.replace(/\r|\n|\u0003/g,"");
// strips all linebreaks from the string, text Animators don't count those

if ( txt[textIndex-1].match(/[0-9\.]/) == null) {
value;
} else {
0;
}


(I’ve also included the period)

[Filip Vandueren]

Follow-up…

I’ve just discovered that since After Effects 16.0
starting an expression with posterizeTime(0); will force it to be only executed once.
So no need for helper-comps and valueAtTime(0)

[Filip Vandueren]

Here’s my solution for HTML-parsing a text, as previously posted on the cow.

https://we.tl/t-uWFHgVPymS (now updated for Javascript engine)

If you write a text like:

hello crazy world.

The expression will apply the text-animator named “b” to everything between and

You can create as many different tags and text-animators as you need.