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rotation acceleration

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Warren Morningstarrotation acceleration
by on Oct 13, 2009 at 8:47:44 pm

I want to animate a propeller so that it starts from a stopped position and then rotates and accelerates so that it becomes a blur (like an engine starting on an airplane). Suggestions? Thanks for the help to a newbie.

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Dave JohnsonRe: rotation acceleration
by on Oct 13, 2009 at 9:07:22 pm

I did this kind of effect a few years back with only some minor adjustments to an expression from either Dan Ehbert's site or AE Enhancers ... I don't recall the details so I'm sorry I can't be more help in that way. However, I'll make one simple suggestion that I unfortunately remembered the hard way so that it might save you the grief I went through ... if you plan to have a sound track, you might want to mix it first, then build your animation to match it ... sound goes a long way in selling some effects, but sound that doesn't sync well with the visuals can also ruin otherwise good visuals.

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Paul ConigliaroRe: rotation acceleration
by on Oct 13, 2009 at 9:22:53 pm

Would you be able to use the graph editor to get a decent acceleration curve?

Also, I'd highly recommend having a propeller element that's already blurred. Many times, motion blur in AE doesn't exactly yield the results you might want.

What I would do is use the graph editor to get a nice acceleration curve, then possibly add a light wiggle expression to give it a little variance. Then I'd transition that into a blurred propeller with some rotation (both directions, look at some reference footage) and a high-frequency wiggle so you have more control over what the blurred propeller looks like instead of relying on the sub-frame samples in AE.

Adobe CS3, Apple FCS2
[Disclaimer: Sometimes I am an idiot and misinterpret people's posts. I'm sorry.]

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Brian CharlesRe: rotation acceleration
by on Oct 14, 2009 at 1:04:36 am

Or use an expression for rotation. time*100 (insert value you want)

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Warren MorningstarRe: rotation acceleration
by on Oct 14, 2009 at 11:44:24 am

Thanks Paul, Brian, and Dave. Great suggestions all. Really appreciate the help.

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Anders HattneRe: rotation acceleration
by on Oct 14, 2009 at 2:40:09 pm

For the expression I'd tie a slider to the value so that way you can make the acceleration with the slider and once you have the speed you want you'll need no more keyframes.

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Steve RobertsRe: rotation acceleration
by on Oct 15, 2009 at 2:36:55 pm

I second the "blurred prop image" recommendation. AE's motion blur might give you a spirograph effect, which you may or may not want.

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