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Alpha triggers animation
Hello
I have a comp with two layers. One is a precomposed animation. The other is a layer with an animated mask shape.
I’d like the precomp animation to start and play when the alpha of the 2nd layer is on beneath it.
I found on this forum an expression which launches an animation when a checkbox is switched on, but I can’t get to modify it to work with the alpha detection…
Thx
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2 Replies
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Play with this and see if it does what you want. It’s set up to drive the Time Remap property of the precomp:
L = thisComp.layer("alpha layer");
threshold = 0.00001;
trig = false;
ss = [width,height]/2;
for (f = timeToFrames(); f >= 0; f--){
t = framesToTime(f);
v = L.sampleImage(L.fromComp(toComp(anchorPoint,t),t),ss,true,t)[3];
if (trig && (v < threshold)) break;
if (v >= threshold) trig = true;
}
t = trig ? time - framesToTime(f+1) : 0;
Dan
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That’s exactly it!
I just have to precomposed the “alpha layer” as well.
Thanks a lot!
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