Value at Time expression

[Darby Edelen]

I’m not sure that I have enough information to give you a satisfactory answer. Do you want object B to just immediately appear at a certain position when object A’s opacity is 0%? Do you want it to animate from one position to another as object A’s opacity goes from 100% to 0%?

I’m guessing the latter, but it’s really hard to tell exactly how you want object B to behave based on object A’s opacity.

Do you need object B to follow a motion path to get where it needs to be or should it move linearly?

Darby Edelen

[Dan Ebberts]

This should cause layer B to jump to layer A’s position when layer A’s opacity hits zero. But as Darby points out, jumping might not be what you want.

A = thisComp.layer(“A”);

f = 0;
foundIt = false;
while (f <= timeToFrames()){ if (A.transform.opacity.valueAtTime(framesToTime(f)) == 0){ foundIt = true; break; } f++ } if (foundIt){ A.transform.position.valueAtTime(framesToTime(f)); }else{ value; } Dan

[Brendan Mccullough]

This is a question I’ve found myself asking lately too. How does one change values at a specified time, but using a smooth animation, rather than a drastic jump. I’ve been noodling it, and I’m sure it’s something like:

if(time >= someValue) {
linear(time, time, time+animationDurationInFrames, value01, value02);
}

but I can’t quite grasp what I’m missing.

I was playing with a rotation value today that it would have been nice to have this. I want to rotate between (let’s just say) 0 degrees and 10 degrees over the course of 10 seconds, and then, in 30 frames, I want to complete the rotation back to 0 degrees from 10 degrees, and then continue the move from 0 degrees to 10 degrees over the course of the next 10 seconds.

My gut tells me there’s a modulus equation that’ll get me what I want, but yet again, it’s eluding me. It’d be something like…

duration = 300;
if(duration % 300 == 0) smoothly animate expression that’s probably linear(something);

[Darby Edelen]

The most robust method I can think of would be accessing the value of the property that will drive the animation (in this case opacity) and then updating the position of the current layer along its motion path based on that value:


if(numKeys > 1){
k1 = key(1).time;
k2 = key(numKeys).time;
o = thisComp.layer("Opacity_Layer").opacity;

linear(o, 100, 0, valueAtTime(k1), valueAtTime(k2));
}
else value;


I haven’t tested it, but something like the above should work if applied to a position property.

Darby Edelen

[Ido Shor]

I tried implementing this expression to my comp, but it seems to be very hard for my machine to compute.

any suggestion why might that be?
can it be because the value of my “A” is driven from a random slider?

shame, cause this expression is a keeper.

thanks, Ido.