Calculating actual angle between two vectors in Unity3D

Question

Is there a way I can calculate the actual angle between two 3D Vectors in Unity? Vector3.Angle gives the shortest angle between the two vectors. I want to know the actual angle calculated in clockwise fashion.

Answer 1

This should be what you need. a and b are the vectors for which you want to calculate an angle, n would be the normal of your plane to determine what you would call "clockwise/counterclockwise"

float SignedAngleBetween(Vector3 a, Vector3 b, Vector3 n){
    // angle in [0,180]
    float angle = Vector3.Angle(a,b);
    float sign = Mathf.Sign(Vector3.Dot(n,Vector3.Cross(a,b)));

    // angle in [-179,180]
    float signed_angle = angle * sign;

    // angle in [0,360] (not used but included here for completeness)
    //float angle360 =  (signed_angle + 180) % 360;

    return signed_angle;
}

For simplicity I reuse Vector3.Angle and then calculate the sign from the magnitude of the angle between plane normal n and the cross product (perpendicular vector) of a and b.