Thanks Karsten,
I was going to post that same link this morning for folks. That, BTW, is one of the best discussions and provides a little more than most photographers even might imagine about the subject. The diagrams to go with that are in a PDF
here and explains the Schleimflug line, Scheimflug Rule and Hinge Line and Rule.
There are also 2 wonderful animated diagrams to go with this article.
Including this allows other readers to follow the discussion.
Asher
Thierry, you just beat me to it by seconds. Your diagrams are new to me and very helpful.