Standard practice?: half-hip or jerkinhead gable

[GeneDavis]

With no wifi here, I cannot attach a pic, but I'll try to be clear with my question.

 

The roof design has two half-hipped gables (a.k.a. "Jerkinhead" roof), the pitches all same, the short hips crossing the gable walls at about the 1/3 points on one, more like 40-20-40 ratio the other.

 

in plan view, does one dimension for location of these hips

 

a) where the hip line intersects the building line (outer framing layer line), or

 

b) where the hip line ends at roof edge.