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Link Opacity to Y Position in Comp
Hello!
I am pretty new to expression in AE, so forgive my ignorance, but I have been combing the internet for an hour trying to find help to solve this problem and haven’t had any luck. So here it goes.
I have a very long column of text layers that I am animating to scroll upwards using a null. I need each line of text to fade in at a certain point on the screen, and then to fade out at another point so that only a few lines are visible at a time.
I’m running into a block because the position is animated entirely by a parent null, and the speed increases to a fast enough pace that doing it manually wasn’t working.
I found some expressions linking opacity to distance from a 3D camera and I think a modification of that might work in my situation, but I haven’t been able to figure it out.
I hope one of you geniuses knows what’s up.
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6 Replies
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try this:
opacityMin = 0;
opacityMax = 100;fadeInStart = 600;
fadeInEnd = 500;
fadeOutStart = 300;
fadeOutEnd = 200;y = toComp(anchorPoint)[1];
if (y <= fadeOutEnd || y >= fadeInStart){
opacityMin;
}else if (y < fadeInStart && y > fadeInEnd){
linear(y, fadeInEnd, fadeInStart, opacityMax, opacityMin);
}else if (y < fadeOutStart && y > fadeOutEnd){
linear(y, fadeOutEnd, fadeOutStart, opacityMin, opacityMax);
}else{
opacityMax;
}Kevin Camp
Art Director
KCPQ, KZJO & KRCW -
i should have added that the fade values (fadeInStart, etc) are in pixels. they define the area that the lines will be at maximum opacity, minimum opacity or interpolate (fade) between those values.
Kevin Camp
Art Director
KCPQ, KZJO & KRCW -
Ok wow great this sounds like exactly what I need. Will it still work even though the position of the actual text layer isn’t changing, just the position of the null it’s parented to is?
And also it’s giving me an error on the expression at line 11. Is there something I’m missing?
Thank you so much!
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“Error at line 11 in property ‘Opacity’ or layer 60
Expected: ).”I tried adding . after the ) on what I think is considered line 11 but I’m still getting the error.
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the expression code box converted all the < > (greater than less than signs) to < and > (html tag equivalents).
i’ll try pasting this as preformated text:
opacityMin = 0; opacityMax = 100; fadeInStart = 600; fadeInEnd = 500; fadeOutStart = 300; fadeOutEnd = 200; y = toComp(anchorPoint)[1]; if (y <= fadeOutEnd || y >= fadeInStart){ opacityMin; }else if (y < fadeInStart && y > fadeInEnd){ linear(y, fadeInEnd, fadeInStart, opacityMax, opacityMin); }else if (y < fadeOutStart && y > fadeOutEnd){ linear(y, fadeOutEnd, fadeOutStart, opacityMin, opacityMax); }else{ opacityMax; }Kevin Camp
Art Director
KCPQ, KZJO & KRCW -
Oh… lol. Now it works!
Thank you for helping me with this so kindly. I really, really appreciate it. I will learn enough about expressions to not sound like a doofus one day! For now, you saved my evening. 🙂
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