Limiting Expressions Duration

[Dan Ebberts]

I’m not sure exactly what you mean, but play around with this scale expression. The first line defines how long it takes each layer to scale up.

scaleTime = 1;

t = (index-1)*scaleTime;
ease(time,t,t+scaleTime,[0,0],[100,100])

Dan

[Cameron Crook]

Basically, I have a bunch of layers that I want to scale to 100% 1 after another. I would normally keyframe each’s scale, however, it would be extremely tedious plus i would have to change all the keyframes again if I wanted to change how long it would take for them to scale up. I attempted to do this using if statements but for some reason they didn’t work, the objects scale continued to increase without stopping.

if(transform.scale==100){100}
else{time*25}

[Dan Ebberts]

I think the reason your expression doesn’t work the way you want it to is that any time an expression references the value of the property hosting the expression, what you get back is the pre-expression (ie, keyframed) value, not the value previously calculated by the expression. So trying to get an expression to stop by checking the value of the property doesn’t work.

I think this change to the expression I cooked up before is pretty close to what you’re after, depending on how your comp is structured (mainly where the scaling layers are in the layer stack):

scaleTime = 4;
t = (index-1)*scaleTime;
ease(time,t,t+scaleTime,[0,0],[100,100])

Dan

[Kevin Camp]

i think you may want to use a valueAtTime expression… that way you can have one layer with the keyframes and the others will just use valueAtTime to reference that animation, but with a time offset.

i assume that ‘newer’ layers will be layered on top/above the first layer to scale up… if so something like this may work for all the other layers:

target=thisComp.layer("ControlLayer");
lastKey=target.scale.key(target.scale.numKeys);
target.scale.valueAtTime(time-(lastKey.time*(target.index-index)));
the ‘target’ layer would be your first layer, the one with the scale keyframes. each layer above it with that expression will scale up sequentially… ie the second layer to scale will be the layer directly above the target,the next layer to scale will be one above that, etc…

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW