seedRandom expression changes results when duplicating comp

[synthetick]

Hi, I’m trying to do something with AE Expressions and they’re not behaving the way I expected. Any Expressions gurus who can advise me? The problem is with seedRandom. My expectation is that if I make a duplicate of this comp, the randomness shouldn’t change because I am using seedRandom. But it does change, and I don’t want that. Did I code something wrong?

[Dan Ebberts · Accepted solution]

I don't think there's a good way to do that. Under the hood, I think the comp id gets factored into the seedRandom calculation. You might be able to use wiggle(), like this, which should give the same result in each duplicate comp:

seedRandom(index,true);
w = rotation.wiggle(0,1)-rotation;
diameter = 2500 + (w/2)*4500;
[diameter,diameter]

[synthetick]

Thank you! I have used your expression and I can now duplicate the comp without the randomness changing 🙂

[Rick Gerard]

Even though you give the seed a value and change it to Timeliess = true, the random function still generates a random number. You will need to convert the expression to Keyframes using the Keyframe assistant to make duplicate comps that have the same look.

[Mylenium · Accepted solution]

Not really. The whole setup is designed wrongly from the outset. It would be easy enough to just consistently generate the values in a master comp/ dummy comp and remote-link them to the sub-comps. There is no requirement to convert anything to keyframes.

Mylenium