Is Vector3 == operator broken?

[rmarra07]

I know this sounds like a stupid question, as it seems pretty unlikely that something as fundamental as Vector3 could have such a huge bug in it that no one has noticed. I’m hoping someone can point out an obvious mistake I’m making.

I’m trying to compare two Vector3 for equality. In this specific example, I’m expecting both to be (0, 180, 0).

public Vector3 RightRotation = new Vector3(0, 180, 0);

private void Move() 
{
   Debug.Log("Rotation: (" + transform.rotation.eulerAngles.x + ", " + transform.rotation.eulerAngles.y + ", " + transform.rotation.eulerAngles.z + ")" + ", Rotation: (" + RightRotation.x + ", " + RightRotation.y + ", " + RightRotation.z + ")" + "; Equal: " + (transform.rotation.eulerAngles == RightRotation));
   if (transform.rotation.eulerAngles == RightRotation)
   {
      Debug.Log("They are equal.");
   }
}

When run this outputs the following to the console:

Rotation: (0, 180, 0), Rotation: (0, 180, 0); Equal: False

I am printing the individual floats here so there is no rounding taking place. The y values of both vectors are exactly 180. Yet, == returns false.

The documentation for Vector3.== says:

Returns true if the vectors are equal.
This will also return true for vectors that are really close to being equal.

It seems to me that something is not working right here.

[Bunny83]

The operator is implemented like this:

public static bool operator ==(Vector3 lhs, Vector3 rhs)
{
    return Vector3.SqrMagnitude(lhs - rhs) < 9.99999944E-11f;
}

and SqrMagnitude looks like this:

public static float SqrMagnitude(Vector3 a)
{
    return a.x * a.x + a.y * a.y + a.z * a.z;
}

So if something is broken than it would be plain floating-point-math. I guess that ToString will round the value. The eulerAngles property is not a good source for exact comparisons. Also watch out, it works differently in edit mode. In edit mode Unity uses a cached value internally. At runtime it’s purely calculated from the quaternion which will never be 100% exact.

[Jessy]

You can’t expect that kind of precision out of Transform.eulerAngles. Rotations aren’t actually stored as Vector3s. Try comparing the Quaternions, or make your own Equals extension method that takes your own tolerance as a parameter.