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animating arrows with expressions

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Tine Lenart
animating arrows with expressions
on Sep 26, 2012 at 6:37:19 pm

Hello there!

I am working on a video project about car driving and I have to add a animation about forces on the tire. I have to demonstrate how the forces work when the car's tire turn left or right (this force is demonstrated on x axis). When the car accelerates or breaks (this force comes to y axis). On top of that, I want to add a third animated arrow, which is the result of the x and y axis. I would like the arrow to have a constant size head, only want to change the length of the body. Anyone can help me please?

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Dan Ebberts
Re: animating arrows with expressions
on Sep 26, 2012 at 9:49:44 pm

It's hard to know exactly what you need (so much depends on the details of your project), but the magnitude of the rsulting force will be:

xyForce = Math.sqrt(xForce*xForce + yForce*yForce)

and the angle will be:


If you wanted to scale the width of the arrow body based based on the xyForce value, you'd have to pick a force that equates to 100% scale and then you end up with an expression like this:

force100 = 500;

Of course the scale expression would need the xyForce value, so you'd either have to calculate that in a slider or duplicate the calculation in the scale expression.

That's probably not much help, but maybe it will get you headed in the right direction.


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Tine Lenart
Re: animating arrows with expressions
on Oct 1, 2012 at 10:30:51 pm

Hello Dan!

I found your code very useful! As I was new to expressions, I had to read a few tutorials and use some of your code. It works very well and I use the dynamic link with my after effects composition, so I can change the value of the x and y force on two sliders.
Thank you!

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