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Forums Adobe After Effects Expression to simulate a pixie flapping it’s wings

• # Expression to simulate a pixie flapping it’s wings

2 Members · 4 Posts
• ### joseph wilkins

June 16, 2021 at 10:43 pm

I have two wings that are on two separate layers – both under the person.

I have 3D turned on and want to get an expression that flaps them at near humming-bird speed.

I’m playing with wiggling the Y rotation of each wing without much luck. Nothing looks fast enough or real enough.

Does anyone have an expression they can share? Thanks!

• ### Kevin Camp

June 16, 2021 at 11:56 pm

This may work for you, just add it to the rotation axis that you want the wings to rotate on.

`upRot = 45 ;dwnRot = -45 ;freq = 10 ; // times per sec ease( Math.cos( time * 2 * Math.PI * freq ), -1, 1, upRot, dwnRot )`

The upRot and dwnRot values are essentially the min and max rotations for the wings (set as needed). Then adjust the freq of the flapping — according to the internet, a humming bird beats it’s wings between 10 and 80 time a second.

If you wanted to add some randomness, you can literally add some wiggle() to the end of the last line:

`ease( Math.cos( time * 2 * Math.PI * freq ), -1, 1, upRot, dwnRot ) + wiggle( 5, 10 )`

• ### Kevin Camp

June 17, 2021 at 1:56 am

Actually, to make the upRot the maximum upwards angle, I should have use the sine function… the last line should be like this:

`ease( Math.sin( time * 2 * Math.PI * freq ), -1, 1, upRot, dwnRot )`
• ### joseph wilkins

June 17, 2021 at 12:29 pm

Thank you SO much! 🙂

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