Character movement relative to camera doesn't work the way I intended.

Hey,

I'm working on a third person character controller with a camera that orbits the character. The camera can be moved around as well as above the character. After lots of trial and error I figured out how to get movement relative to the current position of the camera, however, my code has an unintended side-effect. When I move the camera above the character then "forward" is directed towards the ground, which makes sense but is entirely unproductive. Is there a way to solve this? I feel like a good way would be by accessing the rotation of the pivotpoint which my camera is attached to. How can I do that?

Here's the code I'm using

     float UpdateMovement()
     {
         // Movement
         float x = Input.GetAxis("Horizontal");
         float z = Input.GetAxis("Vertical");
         Vector3 inputVec = new Vector3(x, 0, z);
         inputVec = Camera.main.transform.TransformDirection (inputVec);
         inputVec *= runSpeed;
         controller.Move((inputVec + Vector3.up * -gravity + new Vector3(0, verticalVel, 0)) * Time.deltaTime);
 
         // Rotation
     if (inputVec != Vector3.zero)
         transform.rotation = Quaternion.Slerp(transform.rotation,Quaternion.LookRotation(inputVec), Time.deltaTime * rotationDamping); 
         return inputVec.magnitude;
 
     }