Opacity ON/OFF expression

[Lord Scales]

Weel, this expression will not offer you many control, but try this Dan Ebberts script (I changed it for work in Opacity):

holdTime = .5; //time to hold (seconds)

seed = Math.floor(time/holdTime);
seedRandom(seed,true);
Math.round (random())*100

More info about the script in: https://www.motionscript.com/mastering-expressions/random-1.html

[Craig Wall]

There are many more qualified to answer than me, but I’ll give it a shot.

You would use a wiggle expression.

You would set a very low frequency…so that your subject doesn’t look like he/she’s enduring an epileptic fit.

As I understand any value returned that exceeds 100% would still equate to 100% which could work to your advantage…(The opposite would be true, I believe a negative value would return 0) You could use simple multiplication or division to push your opacity to the two extremes 0 and 100.

Alternatively I wonder if you can wiggle a hold on and off.

Here is an adjustable/very flexible wiggle expression

tweak this…

wigfreq = 30; //wiggle frequency
wigamt = 30; //wiggle amount
wigdetail = .025; //detail of noise
wiggle(wigfreq, wigamt, wigdetail)

What I have provided but stick around and someone will give you a more succinct and more refined answer.

[Lord Scales]

Maybe it would be better to create a Checkbox (Effect > Expression Controls > Checkbox Control) and create this expression for the eye’s opacity:

if (thisComp.layer(“Blinking control”).effect(“Checkbox Control”)(“Checkbox”) == 0) 0 else 100

Animate the Checkbox to get the blinking effect.

[Bruno Meira]

its possible to do that with slider control? for control multiple comps? thanks!

[Jay Mueller]

Thanks. This works great for turning on and off render intense layers will setting up the comp.

[Greg C neumayer]

This is a pretty old post, but still valuable for expressions. Here’s a script get something to flicker/blink.
If you put the opacity at 50%, it will randomly blink on/off.
If you put two keyframes from 100 to 0%, it will transition with flickering instead of a smooth fade, like a light burning out.
If you don’t use any keyframe and set the opacity to 70%, with a flicker frequency of 100, it nicely approximates an eye blink.

Cheers!
-Greg @ Antifreeze Design

//--Flicker On
//Make something flicker to 100% opacity instead of fading in
//Adjust this flicker frequency to your taste
flickerFrequency = 150;

op = value;
if(op > 0 && op < 100){
reverseAmt=100-transform.opacity;
wiggledAmt=wiggle(flickerFrequency,reverseAmt);
roundedAmt=Math.round((wiggledAmt/100));
roundedAmt*100;
}
//--end Flicker On