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Making a follow path speed dependent on y-position
Hi forum
I´m all new to After Effects – using CS6.I have this animation of a plane going in a parabolic path, that I have made using a path made in illustrator, and a plane that follows the path.
The problem is that the speed of the plane is constant. I need the y-axis speed to depend on the position, so that the speed depends on v(y)=sqrt(2*g*y), so it slows down on top of the parabolic path.
Is there any way to achieve this? Have been looking into expressions, and figure that might be the way to go, but dont know if I can combine expressions with a followed path. Thanks in advance for any advice.
Best regards
Søren -
2 Replies
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You don’t really need an expression, you can keyframe the motion to slow down and speed up along the path.
On the other hand, if you need an accurate result, you don’t need a motion path, you can do it with expressions only. Acceleration isn’t one of the most straightforward things to do with expressions, as it requires you to calculate all preceding frames up to the current time, but it can be done. Here’s the basic idea, perhaps you can modify it to suit your needs:
https://forums.creativecow.net/thread/227/12411
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Hi Kalle!
Thank you for your response. In the mean time I ended up making the plane follow the path and slowing down portions of the video – it did the trick – but wasn´t very elegant.Actually I did the expression way as well for another clip in which it wasnt necessary to slow down the motion. It worked perfectly – although there was issues when scaling the size of the compilation. Thanks again Kalle!
-Søren
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