How to get 0-360 degree from two points

Question

Is there a function that will return degrees (0-360) from one point (x = 0, z = 0) to another point (-x = 3, -z = 5)

alt text

Edited to add exact code snippet that worked for me.

 GameObject target = GameObject.Find("Name Of Game Object In Hierarchy");

 float MyPositionX = transform.position.x;
 float MyPositionZ = transform.position.z;
 float TargetPositionX = target.transform.position.x;
 float TargetPositionZ = target.transform.position.z;

 degree = FindDegree(MyPositionX - TargetPositionX, MyPositionZ - TargetPositionZ);   

  public static float FindDegree(float x, float y)
  {
      float value = (float)((System.Math.Atan2(x, y) / System.Math.PI) * 180f);
      if (value < 0) value += 360f;
      return value;
  }

Answer 1

Best Answer

Answer by YoungDeveloper · Aug 20, 2015 at 07:42 PM

This will take classic x and y

 private void Start(){
     Debug.Log(FindDegree(0, 1));
 }
 
 public static float FindDegree(int x, int y){
     float value = (float)((Mathf.Atan2(x, y) / Math.PI) * 180f);
     if(value < 0) value += 360f;
 
     return value;
 }

If you want to use this from transform positions, then vector3.angle is what you are looking for. As you have to know what is forward to calculate it, i believe there even a ready example if you google.

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Bunny83 · Aug 20, 2015 at 10:10 PM 0

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btw: $$anonymous$$athf does also have a PI constant as float, so that casting from double to float wouldn't be necessary. There are also two conversion constants:

Those are factors so you just have to multiply an angle in radians with "$$anonymous$$athf.Rad2Deg" to get degrees.

Also keep in $$anonymous$$d that the parameters of the Atan2 method are swapped. The parameters are y and x. The example on the docs page is actually wrong ^^. They are swapped because it actually calculates the arctangent of "y / x" and in addition takes the quadrant into account by looking at the signs of x and y. It also handles the case of "x == 0" to prevent a division by 0. See wikipedia as well.

YoungDeveloper · Aug 21, 2015 at 10:33 AM 1

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@Bunny83 I actually use my own $$anonymous$$ath lib, where i have my own constant PI. It was actually a typo from my side using $$anonymous$$athf.Atan2 i meant $$anonymous$$ath in this example. As i share my libs in various c# projects i never use unity $$anonymous$$athf lib, as its pretty much a wrapper around System.$$anonymous$$ath. For example here's a source for $$anonymous$$athf.Atan2().

 public static float Atan2(float y, float x){
     return (float)$$anonymous$$ath.Atan2((double)y, (double)x);
 }

So we have ton of casts here, what i do in my libs is usually calculate evetyhing and only then cast once. But even that down cast is zero overhead, as its pretty much a number cut down, not even a round.

What comes to the function i posted, i know about atan swap, but if I swap Atan2 correctly , just like docs say, it actually produces mirrored results for x axis. I did tests with these examples, and results are perfect. ;)

 Debug.Log(FindDegree(0, 0));   //0 - 360
 Debug.Log(FindDegree(0, 1));   //0 - 360
 Debug.Log(FindDegree(1, 1));   //45
 Debug.Log(FindDegree(1, 0));   //90
 Debug.Log(FindDegree(0, -1));  //180
 Debug.Log(FindDegree(-1, -1)); //225
 Debug.Log(FindDegree(-1, 0));  //270
 Debug.Log(FindDegree(-1, 1));  //315

Bunny83 · Aug 21, 2015 at 11:20 AM 0

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@YoungDeveloper: I know that Unity's $$anonymous$$athf class is just a wrapper for System's $$anonymous$$ath class. I didn't ment the cast overhead but the cast just makes it harder to read ^^. That's actually the reason why Unity provided that wrapper class for $$anonymous$$ath since Untiy only works with floats ins$$anonymous$$d of doubles.

If you use your own $$anonymous$$ath lib (or System's one) you should do:

 public static float FindDegree(double x, double y){
     double value = ($$anonymous$$ath.Atan2(x, y) / $$anonymous$$ath.PI) * 180;
     if(value < 0d) value += 360d;
     return (float)value;
 }

to $$anonymous$$imize casting and precision problems. Since your x and y are casted to double anyways you can simply define your parameters as double. ints and floats are implicitly casted to double.

$$anonymous$$irrored results? In mathematics the unit circle has 0° on the right and goes counter clockwise around the circle.

  x, y
  -----------
  1, 0 -> 0°
  1, 1 -> 45°
  0, 1 -> 90°
 -1, 1 -> 135°
 -1, 0 -> 180° // or -180°
 -1,-1 -> 225° // or -135°
  0,-1 -> 270° // or -90°
  1,-1 -> 315° // or -45°

The given angle should result in this vector:

 Vector2(Cos(angle), Sin(angle))

Which is the "opposite" operation of Atan2.

$$anonymous$$eep in $$anonymous$$d this is a pure mathematics function and definition. In the context of Unity everything is a bit different since in mathematics you usually work with a right-handed system while Unity uses a left-handed system. Likewise as you might know there are many different diffinitions for Euler angles and Unity only uses one of them ^^.

YoungDeveloper · Aug 21, 2015 at 11:35 AM 1

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@Bunny83 yeah thats exactly what i do in my libs, i tried to write it fast unity style for the op lol.

Tovey-Ansell · Nov 15, 2016 at 03:21 PM 0

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Sorry to dig up an old thread, but this just wont work for me...

I have the exact same FindDegree method, but when giving it the values 0 and 25, it returns 0 as the angle? Has something changes since to make this method not work any more?

calebaker Tovey-Ansell · Nov 15, 2016 at 09:05 PM 0

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That's actually correct, if you drew a line from 0 strait up 25 units, the degree to that point from 0 would be 0 degrees or 360 degrees.

Answer 2

Answer by eppz · Feb 15, 2017 at 12:39 PM

I made an extension, use like this:

 float angle = transform.position.AngleTo(touch.position);

Just put this into a CS file somewhere:

 public static class _Vector2
 {
     public static float AngleTo(this Vector2 this_, Vector2 to)
     {
         Vector2 direction = to - this_;
         float angle = Mathf.Atan2(direction.y,  direction.x) * Mathf.Rad2Deg;
         if (angle < 0f) angle += 360f;
         return angle;
     }
 }

This is not (!) mirrored, as Atan2 takes y coordinate first.

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PabloCorso · Oct 03, 2017 at 01:19 AM 1

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This is great.

How to get 0-360 degree from two points

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