I'm trying to get the angle between two 2D vectors relative to the first vector input. Every method I've tried has given me a value between 0-180 degrees but doesn't tell me whether it was a clockwise or counter-clockwise rotation.
For example: If I hold my forward vector in a variable and then turn counter-clockwise 45 degrees and use that as my second forward vector, I'm looking for -45 or 315 degrees as the output, not 45.
float AngleBetween(Vector2 a, Vector2 b) { // Get a vector rotated 90 degrees from a. Vector2 perpendicular = new Vector2(a.y, -a.x); // Compute a scaled projection of b onto the original and rotated version. float x = Vector2.Dot(a, b); float y = Vector2.Dot(perpendicular, b); // Treat these as a point in a coordinate system where a is the x axis, // and perpendicular is the y axis, and get the polar angle of that point. return Mathf.Atan2(y, x); } There is a solution for unity (Maybe there is a better solution, but it works):
using System.Collections; using System.Collections.Generic; using UnityEngine; public class NewBehaviourScript : MonoBehaviour { void Start() { var v1 = new Vector3(1, 1, 0);//45 var v2 = new Vector3(1, 0, 0);//0 Debug.Log(GetDegree(v1, v2)); Debug.Log(GetDegree(v2, v1)); } private float GetDegree(Vector3 from, Vector3 to) { var rot = Quaternion.FromToRotation(from, to); var angle = 0.0f; var axis = Vector3.zero; rot.ToAngleAxis(out angle, out axis); if (Vector3.forward == axis) { return angle; } else { return angle - 360f; } } } Output:
-315 44.99999 