Animate the stars -random flicker effect

[jcalcina]

Say I wanted to make eight of the bigger stars flicker seemingly at random. Is there a way I can do that without having to make eight different files?

Would I apply an expression at eight different anchor point locations within the same pre-comp? Is that possible?

Thanks.

[Mike_Abbott]

That very much depends on how your sky has been created. Are the large stars invididual layers or what? A screenshot of your precomp timeline and comp window might help.

[jcalcina]

The larger stars are a separate png file with a transparent background.

[Mike_Abbott · Accepted solution]

Alt click the stopwatch for the opacity property for each star layer. Add this expression:

wiggle(4,100)

Adjust the nubers to taste. first number is frequency per second, second number is amplitude.

--- EDIT ---

I think I misunderstood - reading your message again I now think your 8 large stars are on a single layer. Yes?

In that case - a different approach. Set up layers as follows:

1. Solid layer. Apply turbulent noise effect - adjust settings (contrast, complexity, scale etc) so you have random patches of white and black. Animate the evolution property so the pattern changes over time.

2. Your star layer

Create a Luma track matte between these layers.

Your stars will now vary in opacity over time.

[jcalcina]

Thanks Mike...looking forward to following up on this, it is the varied effect I would be looking for.

[P.M.B]

Here's another method using fractal noise as a trkMat.

Make Stars Twinkle! | After Effects Tutorial - YouTube

Sorry,  I missed Mike's edit

[jcalcina]

Thanks...great tutorial.

[jcalcina]

Hi guys...the track matte method seems involved and heavy on resources? I could be wrong. But are there bandwidth considerations per different methods of animating?

[Mike_Abbott]

There shouldn't be any problems at all with a very simple track matte like this - it's everyday stuff.

There are two very similar nose effects - fractal noise and turbulent noise, you could use either. Fractal noise is older and slightly more processor intensive, but GPU accellerated.  It might be that you're experiencing a GPU related  issue. Check your project settings and see if you are using GPU to accelerate effects. if so, turn it off by changing it to software only and see if that helps.

[jcalcina]

Ok thanks