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Expression to invert the opacity of a layer based on another
Hi guys
Im pulling my hair out at what should be a simple expression but no matter how hard i think, i just can’t get my head around it and need some help please.
I have a layer (layer 1)that has to have its opacity at 100% throughout the comp. At certain times during my comp, another layer (layer 2) has it opacity at 100. This layer has markers on it that represent opacity at 100%. At all other times its at 0%. So what I need is layer 1 to be 0% at the markers or similarly, when that layer is at 100%. So basically it just needs to invert.
At the moment my expression is linked to layer 2s opacity +100
This should be simple but i can’t figure it out.
Thanks for your help
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5 Replies
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If A=100, B=0.
If B=0, A=100.
Assuming … if A=25, B=75, if A=85, B=15.Therefore A+B=100
… and B=100-A. -
Hi Dave
For a number of reasons really. Im trying to get more into expressions and the more i do the more i learn. it keeps my comp nice and neat and manageable and in my comp, i have a layer with nearly 85 markers. At every marker, i need layer 1s opacity to be at 0%. Although your solution is a very good one, id rather avoid it.
As it turns out, i stepped away from my machine, had a coffee and came back and it came to me. All i had to do was to multiply the opacity by -1 the add 100. It works just fine now.
Thanks for your reply though. I appreciate all help on this great resource, the Cow.
Chris
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(-1*a)+100 is the same as 100-a, no? 😉
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This If statement seems to do what you want, on the other layer’s Opacity:
op = thisComp.layer(“2s”).opacity;
if (op < 100) 100 else 0 Assuming the contolling layer is named "2s". Dan explains if statements here: https://www.motionscript.com/mastering-expressions/language-beginning-4.htmlSo anytime layer 2s’s opacity drops below 100, the layer with the expression’s opacity will be 100. If layer 2s is at 100, the other layer will be at 0.
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This linear interpolation on Opacity, does the same thing:
op = thisComp.layer(“2s”).opacity;
linear(op, 0, 100, 100, 0)Well, it’s not really the same thing, it gives you the inverse opacity of layer 2s. It just says as the opacity of 2s (op) changes from 0 to 100, change the opacity of this layer from 100 to 0.
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