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Activity Forums Adobe After Effects Expressions Z Rotation to Speed Expression

  • Z Rotation to Speed Expression

    Posted by Tim West on July 5, 2012 at 4:57 pm

    Hi,

    I’m trying to write an expression for a slider to control the speed of a layers Z rotation so I can control the how fast it spins during an animation – e.g. a bike wheel which slows when it travels up a ‘hill’ but speeds up when it descends.

    Can anyone recommend a method or point me in the direction of achieving this via expressions & sliders?

    Thanks,

    T

    Dan Ebberts
    replied 13 years, 10 months ago
    2 Members · 1 Reply
  • 1 Reply
  • Dan Ebberts

    July 5, 2012 at 6:29 pm

    Controlling rotation speed can be a real pain. Worst case–you have to write an integrating expression that goes back in time, frame-by-frame to calculate what the current total rotation should be. It might be a little simpler, depending on the nature of your speed animation.

    However, would it be easier to calculate distance traveled, and convert that to rotation using 360*(distance/(Math.PI*diameter))?

    Dan

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