Hi Jonathan,
Thanks for the reply,
Very illuminating about it having to be kept perpendicular to the surface (impossible without 5 axis, as you said). I'm hobby level as I said, but it would have been fun trying to write it.
I think my idea, having looked at what you wrote, would result in a stepping effect, is that right?.
Is Tan necessary to roughly accomplish what I'd hoped for or can this all be done using Sin Cos alone?. I'm not into Tan...
Regards
Gareth