Hi Jon,
The hips were drawn using traditional developed drawing techniques. No math. That's what le trait is all about.
Do you have access to some of the French books like "Le Charpente en Bois" or Mazzerolle's "Le Trait de Charpente"? They are available from the Compagnons du Devoir bookstore, and show the techniques very clearly. There are many other books related to the techniques.

You can also look at my five articles entitled "When Roofs Collide" in the back issues of Timber Framing. I learned much of this from the French and Germans.

I also reviewed the following book in Timber Framing #115, and it's available fro a frre download:
The Invisible Tools of a Timber Framer: A survey of principles, situations
and procedures for marking, by Ulrik Hjort Lassen.
Gothenburg, University of Gothenburg, Gothenburg Studies in
Conservation No. 32, 2014. In English. ISBN 978-91-7346-785-8,
8¼ in. x 10¼ in., 238 pages, copiously illustrated. Available as a
free PDF download at hdl.handle.net/2077/35598 or in print from
the publisher by emailing acta@ub.gu.se. Softcover, 212SEK.


Another website: http://www.historicalcarpentry.com/l-art-du-trait.html