[PyMOL] light source position

[kostas]

Hallo everybody

I would like to improve the position of the light source in the figures 
I prepare. I 've realised that the position is defined by the values of 
the three vectors( I assume the position 0,0,0 is the center of the 
object). Instead of modifying the distances for each vector I would 
prefer to have the distance from the object constant ( let's say 
starting from -1 in z) and then shifting this distance in x or y 
dimension by some degrees. I wonder if somebody has developed a script 
for such a purpose. I would also like to explain me what is the 
definition of the direct function.
thanks a lot
cheers kostas