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Random opacity on specific way
Please, I need help with a very specific expression. I have created this screen that is going to work as part of an intro for a series of videos.
I want to make those green squares randomly sort of flicker, by changing the value of the opacity, but it must always go from 0 to 100 or from 100 to 0, across 1 or 2 seconds, which is not what happens if I just use a regular wiggle expression on the property.
The behavior I need is:
– random interval (1 to 3 seconds)
– opacity goes from 0 to 100 in 1 or 2 seconds (30 fps)
– random interval (1 to 3 seconds)
– opacity goes back from 100 to 0 in 1 or 2 secondsI have done this manually, by adding certain keyframes and telling them to loopout. As there are too many, you can’t notice it’s a cycle and it gives the illusion of randomness. But I have to manually create this randomness using keyframes at different points for every layer, which can become an exhaustive processes if I intend to keep this line of work for other screens.
I already have each green square on its own layer. Is there a way to make it more automatic through the use of an expression?
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4 Replies
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It sounds do-able, but it seems like there’s info missing. Maybe a more detailed example would help.
Dan
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Sure!
Here, that’s what I did manually:
In this example, as I said, there is no real randomness, for I used keyframes and a loopout expression in a manner that created more or less the same effect.
Can I create this behavior via expression?
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This is a pretty simple version that might get you started:
minFade = .1;
maxFade = .5;
minHold = .5;
maxHold = 1.5;
minDelay = 1;
maxDelay = 1.5;
seedRandom(index,true);
myFade = random(minFade,maxFade);
myHold = random(minHold,maxHold);
myDelay = random(minDelay,maxDelay);
myStart = random(minDelay);
if (time > myStart){
myPeriod = myFade*2 + myHold + myDelay;
t =(time - myStart)%myPeriod;
if(t < myFade)
linear(t,0,myFade,0,100)
else
linear(t,myFade+myHold,myFade*2+myHold,100,0);
}else
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Dan
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Magnificent!
It worked perfectly. Thanks a whole lot, friend!
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