Thank you so much, this helps a lot! Forgot to put in the rhino file, so I will keep that in mind for next. The surface is a simple roof above a sculpture garden. I have done a sunlight analyes with a ladybug script, but unfortunately there is too much shadow on the terrace of this garden. So I wanted to make a script like this to change the width and the height of the controlpoints to enlarge the sunpath on the terrace. This really saves my day.