### Random pulse expression

Posted:

**November 29th, 2015, 2:09 pm**Hey, IÂ´ve googled for hours and can't seem to find any expression that does what IÂ´m after. Also IÂ´m not so great with expressions, so its hard for me to make complete sense of them.

I have about 20 different layers of photoshopped stars in a comp, and I want them all to be twinkling randomly using expressions. I want them to both twinkle and fade in and out randomly like real stars appear to do, not as strobe lights, which is what happens when i try the wiggle() or random() expressions. I want the twinkling and fading to pulsate at random intervals and i also want the length of each "pulse" to be randomized.

The closest solution I have found to the effect i want is this: https://forums.creativecow.net/thread/227/18549

freq = 0.1;

amp = 5;

amp*Math.sin(freq*time*Math.PI*2)

That uses a sine wave formula, which when applied as an expression creates a pulsating effect. However, each sine wave has exactly the same amplitude and frequency, and if I apply this expression to all 20 stars, they all pulse in and out at the exact same times with exact same shine and duration. The "Shine" effect is a good look, but it is a hassle to keyframe each of the 20 stars differently to make it appear convincingly random.

I would really appreciate a swift reply to this! Thank you so much for any help!

I have about 20 different layers of photoshopped stars in a comp, and I want them all to be twinkling randomly using expressions. I want them to both twinkle and fade in and out randomly like real stars appear to do, not as strobe lights, which is what happens when i try the wiggle() or random() expressions. I want the twinkling and fading to pulsate at random intervals and i also want the length of each "pulse" to be randomized.

The closest solution I have found to the effect i want is this: https://forums.creativecow.net/thread/227/18549

freq = 0.1;

amp = 5;

amp*Math.sin(freq*time*Math.PI*2)

That uses a sine wave formula, which when applied as an expression creates a pulsating effect. However, each sine wave has exactly the same amplitude and frequency, and if I apply this expression to all 20 stars, they all pulse in and out at the exact same times with exact same shine and duration. The "Shine" effect is a good look, but it is a hassle to keyframe each of the 20 stars differently to make it appear convincingly random.

I would really appreciate a swift reply to this! Thank you so much for any help!