Transform.Rotate not working around certain axes

Questions & Answers
1

I am trying to write a missile guidance script using proportional navigation. However, I encountered a problem with the Transform.Rotate function in Unity. When rotating around every axis except the Z-axis (0,0,1), everything works as expected (see video, Unity Transform.Rotate confusion - YouTube if this link doesn’t work try the one below). Only when rotating around the Z-axis nothing happens. So far I have narrowed it down to the -90 degrees X orientation I start the rocket with.166484-y-starting-position.png I have no idea what is going wrong here. Can someone please help?

void FixedUpdate()
    {
        Vector3 LOS = target.transform.position - transform.position; //Line of sight (Black)
        Vector3 LOSGain = LOS.normalized - prevLOS.normalized; //Change in LOS (Red)
        float LOSAng = Vector3.Angle(transform.forward, LOS);
        Debug.DrawRay(transform.position, LOS, Color.black);
        Debug.DrawRay(transform.position, LOSGain*10, Color.red);

        Vector3 perpVec = Vector3.Cross(LOS.normalized, LOSGain.normalized); //perpVec is perpindicular to both the LOS and the LOS change

        float rotationSpeed = Mathf.Clamp(Mathf.Abs(LOSGain.magnitude * N), 0, maxAngCorr); //rotationspeed = Omega * N (Clamped to maximum rotation speed)

        transform.Rotate(perpVec, rotationSpeed); //<--Rotate happens here
        Debug.Log("SHOULD BE ROTATING");
        Debug.Log("perpVec: " + perpVec);
        Debug.Log("rotationSpeed: " + rotationSpeed);
        Debug.DrawRay(transform.position, perpVec.normalized * 10, Color.blue);

        prevLOS = LOS;
    }

I have also tried this parallel code and it has the same problem:

Quaternion rot = Quaternion.AngleAxis(rotationSpeed, perpVec.normalized); // rotate with rotationSpeed around perpVec axis.
transform.rotation *= rot;
2

I have found a solution that avoids the problem by doing the rotation in another way:

Vector3 newLookDirection = Quaternion.AngleAxis(rotationSpeed, perpVec) * transform.forward;
transform.LookAt(transform.position + newLookDirection);

However, it would be nice if someone can shine some light on why the other solutions don’t work, but now this one is working flawlessly :slight_smile: