Marker.QuaternionFromMatrix C# (CSharp) Method

    public static Quaternion QuaternionFromMatrix(Matrix4x4 m)
    {
        // Adapted from: http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/index.htm
        Quaternion q = new Quaternion();
        q.w = Mathf.Sqrt(Mathf.Max(0, 1 + m[0, 0] + m[1, 1] + m[2, 2])) / 2;
        q.x = Mathf.Sqrt(Mathf.Max(0, 1 + m[0, 0] - m[1, 1] - m[2, 2])) / 2;
        q.y = Mathf.Sqrt(Mathf.Max(0, 1 - m[0, 0] + m[1, 1] - m[2, 2])) / 2;
        q.z = Mathf.Sqrt(Mathf.Max(0, 1 - m[0, 0] - m[1, 1] + m[2, 2])) / 2;
        q.x *= Mathf.Sign(q.x * (m[2, 1] - m[1, 2]));
        q.y *= Mathf.Sign(q.y * (m[0, 2] - m[2, 0]));
        q.z *= Mathf.Sign(q.z * (m[1, 0] - m[0, 1]));

        // We need to invert rotations on X and Z axis
        q.x = -q.x;
        q.z = -q.z;

        return q;
    }