swift calculating degree of joystick rotation

Question

I'm working on a spritekit game using swift and I implemented a joystick using this library. I'm having a hard time trying to figure out how to calculate the degree of the rotation. the library gives you this information when you move the joystick around

joystick.trackingHandler = { jData in
  // something...
  // jData contains angular && velocity (jData.angular, jData.velocity)
}

I don't need to rotate the player since the game is a 4 directional jrpg style, so i'll just be triggering movement based on a range of degrees.

does anybody have any useful articles or information on turning the velocity returned into a degree?

I've seen people using atan2 but it seems to only accept Double's and the velody returned is of type CGPoint.

Access the `x` and `y` members of `CGPoint` to get `CGFloat`s that you can use with `atan2` — Alexander, May 18 '17 at 04:31
so i tried that, `atan2(data.velocity.x, data.velocity.y)`, but it gives me the same numbers when i print as `data.velocity`. any ideas why? — Shan Robertson, May 18 '17 at 04:35
to be clear, the velocity goes from 0 to 3, and -3 to 0 rotating clockwise. — Shan Robertson, May 18 '17 at 04:39
To be fair, I haven't looked at this framework. Shouldn't you be dealing with the position (that's all you care about, no?) of the joystick, not its velocity? — Alexander, May 18 '17 at 04:44
The docs for that library are very sparse when it comes to using it! But it seems to me that `angular` is the number you are after. — Gary Makin, May 18 '17 at 05:05
i agree, angular is looking like what i need, but how can i convert those numbers into something useful? — Shan Robertson, May 18 '17 at 05:12

score 2 · Accepted Answer · edited May 23 '17 at 10:31

2

The angular value in jData contains the angle in radians.

To convert, use the following code for values between -180 and +180:

let degrees = jData.angular * 360 / (2 * M_PI)

and this for values between 0 and +360:

var radians = jData.angular
radians = radians > 0 ? radians : (2 * M_PI + radians)
let degrees = radians * 360 / (2 * M_PI)

adapted from https://stackoverflow.com/a/1311134/968577

edited May 23 '17 at 10:31

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answered May 18 '17 at 05:35

Gary Makin

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That works perfectly, thank you man! coming from the web to iOS has made me realize how bad at math i am :O – Shan Robertson May 18 '17 at 06:08

swift calculating degree of joystick rotation

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