YawPitchRoll.cs

    public static Quaternion YawPitchRoll(float yaw, float pitch, float roll)
    {
        Quaternion heading = Quaternion.AngleAxis(yaw, Vector3.up);
        Quaternion attitude = Quaternion.AngleAxis(pitch, Vector3.right);
        Quaternion bank = Quaternion.AngleAxis(roll, Vector3.forward);
        return heading * attitude * bank;

        //  transform.rotation *= YawPitchRoll(yaw, pitch, roll);
        /////  transform.rotation *= Quaternion.Euler(pitch, yaw, roll);
        //
        // The Euler() function also applies three independent rotations.
        // There would be a natural expectation that you could use the Euler
        // angles to specify such a straightforward rotation.  However,
        // the order of rotations hardwired into Unity's function will cause
        // a gimbal lock situation and much confusion for the rotations.
        // The built-in Unity ordering for Quaternion.Euler() is Z, X, Y.
        // We want Y, X, Z.
        //
        // (Clarification: there is *always* a gimbal lock situation for
        // applying Euler angles in any order, but which order you choose
        // will determine what scenarios are likely to end up locked with
        // two axes merged into a single pole.  The Unity default ordering
        // is simply not helpful for flight-simulator type applications,
        // so we avoid it with this calculation instead.)
    }