After Effects, Expression : Time + Slider Control (Time*effect("Slider Control")("Slider")

[spnountky]

Hello,

First post here.

I'm having big troubles understanding what's wrong with my simple expression.

What i'm trying to achieve : I want to make a layer rotate with the time. Like this : Rotation = (Time*100)

So like this, at 1 second, the value of rotation will be 100°.

So far so good.

Then, I want to make this rotation stop, and control when it stops.

So i add a slider control.

I put the value on my slider control to 100, and change the expression on my rotation to : Time*effect("Slider Control")("Slider")

So right now, nothing changed.

But then i animate the value of my slider control. One value to 100, move forward in time, add another value to 0.

And now everything goes strange. My rotation goes in positive values and then, in the middle of it, change rotation and goes into negatives values...

I don't understand why it does this, specialy since taken separatly, both function are linear.

If you guys have an idea about this, this would be awesome!

Thanks a lot.

Loick

[Mylenium · Accepted solution]

It's more complicated than that. By simply animating the slider value you are doing an absolute multiplication and even a million multiplied by zero is still zero. You have to integrate the existing values to retain them. read this article of Dan Ebberts' for more detailed explanations and code snippets:

Expression Speed and Frequency Control

Mylenium

[spnountky]

Thanks a lot

Loick