Need some expressions help

[Steve Roberts]

Arctangent, or atan?

https://hyperphysics.phy-astr.gsu.edu/hbase/ttrig.html

[Kevin Camp]

i think it is this:

radiansToDegrees(Math.atan(y/x))

but there may be issues with which quadrant it is in… i seem to remember something about since tangent (or arctangent) can’t be calculated for an angle 90 degrees or greater then that created some issues getting angles that might be in any quadrant other than 1… steve’s link talked a bit about it too.

Kevin Camp
Designer – KCPQ, KMYQ & KRCW

[Jerzy Drozda jr]

Take a look at this tutorial.
https://library.creativecow.net/articles/drozda_jerzy/Radar.php

I’m not 100% sure, but I think I had the same situation when calculating collision detection. Download the project files and take a close look at the expressions used.

I’m sorry I can’t give you the straight answer, but I’ll be traveling all weekend and I’m getting ready for that. I won’t be able to respond for next two days.

I hope you’ll get the problem solved.
Good luck!

Maltaannon

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maltaannon.com – Free After Effects Video Tutorials and more

[Kevin Camp]

ok, atan2 fixes the quadrant issue… so this should work nicely.

radiansToDegrees(Math.atan2(y,x))

where x and y are your calculated values between the 2 points.

Kevin Camp
Designer – KCPQ, KMYQ & KRCW

[Kevin Camp]

playing around with this a little more… if you want it to return a value based 0-360 degrees, this seems to work…

180 – radiansToDegrees(Math.atan2(y,x))

Kevin Camp
Designer – KCPQ, KMYQ & KRCW

[Barend Onneweer]

Hi Moldyboot,

Interestingly, I got as far as “Math.atan2(y,x” before I started the thread, but adding “radiansToDegrees” got me where I need to be.

Basically what I’m trying to do is combine two trackers to track rotation without having to bake the result into keyframes as I would when using AE’s rotation tracker and applying the result to a layer…

Thanks,

Barend

Raamw3rk – digital storytelling and visual effects