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Z Rotation to Speed Expression

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Tim West
Z Rotation to Speed Expression
on Jul 5, 2012 at 4:57:36 pm


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?



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Dan Ebberts
Re: Z Rotation to Speed Expression
on Jul 5, 2012 at 6:29:48 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))?


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