Axis and Angle to Axis and prepndicular Vector

I have a problem.
I need code for Axis and Angle coversion to Axis and prepandicular Vector to Axis.
Now how can you do that ?
(i need it for gluPerspective function for the 3 last arguments (the rool thing))

First, given an angle/axis rotation, there is no one vector perpundicular to that axis; there is a infinite number of perpundicular vectors.

Second, I think you’re talking about gluLookAt, not gluPerspective.

Lastly, gluLookAt needs a direction to be considered ‘Upwards’. Any direction will do as long as it isn’t along the same direction as the look at point.