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Turn Layers on/off with Luma Matte
I’m trying to turn a wall of layers on/off (or individually scale from 0 to 100 to 0) with a luma matte but don’t know where to start. In the image below i want to have simple black/white rings of a circle growing that define which balls are visible…similar to an LED screen.
I’ve had luck with QubaHQ’s light wall tutorial but don’t know how to apply this to layers vs lights.
Any help is appreciated.
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1 Reply
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you could use sampleImage() in each layer’s opacity (or scale) property to sample your luma matte.
to make the expression easier, i would probably convert your luma matt to an alpha with an effect like channel combiner (set from>luminance and to>alpha only).
then the expression for opacity would look like this:
target=thisComp.layer(“luma matte”); // set this to your luma matte layer
target.sampleImage(position, radius = [.5, .5], postEffect = true, t = time)[3] * 100or scale:
target=thisComp.layer(“luma matte”);
s=target.sampleImage(position, radius = [.5, .5], postEffect = true, t = time)[3] * 100;
[s,s]depending on how you want things to work, you could set the sampleImage sample radius to use the layer’s width & height by changing radius to [width/2,height/2].
if you wanted the layer to be eight on or off (nothing in between), you could add a rounding function to the sampleImage value like this:
Math.round(target.sampleImage(position, radius = [.5, .5], postEffect = true, t = time)[3]) * 100
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW
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