Camera Location: (where are you)

X

Look At Vector: (coordinates of the object you want to look at)

X

Look Up Vector: (usually 0 1 0)

X

Viewpoint Orientation (calculated):

First three numbers = axis (unit vector), last number = angle (radians).

The rotation transform the world coord frame into the viewpoint,
with the original negative z axis looking into the direction of the look-at vector.