Start or Stop expression at a given frame?

[GableIsAble]

hello to everyone on the support forum.

I searched the forum but wasn't able to find anything quite good for resolving the matter.

This is something that my IT group Charles Stinson, Nick Carangi, and Sandra Connor have been working on fixing for a while.

I'm getting into expression but the issue is that I am not able to start or stop an expression at a given moment.

I.E. If i want to wiggle(3, 10) until frame 100.

How can I set this up?

Thanks in advance.

After Effects Cs5.5

[Dave_LaRonde]

I can think of a way, but it may not be the most efficient way to do it.  I stink at expressions myself.   You can refer the wiggle values to a layer containing sliders.  Using hold keyframes, set the initial values.  At frame 100, change the slider values to turn the wiggle off.

Or just split the layer containing the wiggle at frame 100, and remove the wiggle expression.

[Rick Gerard]

You could use an if (time < a value) then.... but this gets very unweildly very quickly. As Dave said, the easiest thing to do is to split the layer.

[Todd_Kopriva]

Rick and Dave are correct that it may be easiest to split the layer, but there are examples in After Effects Help for doing this with expressions, here:

http://helpx.adobe.com/en/after-effects/using/expression-examples.html#expression_example_start_or_s...

[Dan Ebberts]

If you want it to hold the last wiggle value, I'd do it like this:

stopFrame = 100;

t = Math.min(time,framesToTime(stopFrame));

wiggle(3,10,1,.5,t)

Dan

[Mathias Moehl]

If you are willing to purchase an additional extension, my Expression Timeline is a generic solution to limit expressions to a specific range, fade them in and out and even transition from one expression to another one.

Expression Timeline 2 - aescripts + aeplugins - aescripts.com

[lukak72401968]

With all those expressions, cluttered timeline, disfunctional graph editor, AE looks sooo medieval... Wothout 3rd party tools it's getting unusable... 

[electropithecus]

Thanks so much for this! Super useful; I have an animation that's supposed to show a bunch of molecules swirling around in a solution, then after a time one of them moves and binds to a receptor, stopping completely. This is perfect.

[angie_taylor · Accepted solution]

Add your wiggle

Create a new Null called "Control Layer"

To this add two Expression Control sliders, rename one "frequency" the other "amplitude"

Click on the padlock button in the effects Control panel to keep this visible for the next step

In the expression ass two new lines before wiggle and type;

f=

immediately drag the pickwhip from the expression to the "frequency" effect slider

add a semi colon after this

add a new line and type;

a=

immediately drag the pickwhip from the expression to the "amplitude" effect slider

add a semi colon after this

the next line should be your wiggle and it should read;

wiggle(f,a)

the entire expression should look something like this;

f=thisComp.layer("Controller").effect("frequency")("Slider");

a=thisComp.layer("Controller").effect("amplitude")("Slider");

w=wiggle(f,);

Now you have two sliders to control the frequency and amplitude of your expression

You can animate them to start and stop wherever you like

you can interpolate values or if you want values to suddenly change, Toggle Hold the keyframes

Here's a tutorial that will help you with this;

Setting variable wiggle values

[ChiliChili]

The best and simpliest solution what I finded. Many thanks, great!