gluLookAt - upVector Problem

Hi Folks!
I have problems using the upvector-parameters of gluLookAt(…).

I have my camera positioned at the center (0,0,0) and it should face an object (x,y,z).
The Objects position always changes, so do I have to change my upvector too, because it´s the normal-vector to the vector between my oject and cameraposition (???)…
How is it meant?? Anybody please…
Thanks in advance!

if your upvector shall always be orthogonal to your view vector yes
if not no

depends on what kind of camera you want to simulate

The up vector is not required to be perpendicular to the camera’s direction but if you try to look in the direction of the up vector, you will have problems.