1. A method which may be applied by a computer ( 10 ) for creating, from a first axisymmetrical surface ( 30 ) a second surface ( 40 ) belonging to a sub-system of a complex system, this second surface having to observe at least one constraint ( 24 , CM), this method including: a step (E 20 ) for modeling said first axisymmetrical surface ( 30 ), while observing said constraint ( 24 , CM), with at least one parameter (P), this modeling step (E 20 ) including: a discretization sub-step (E 23 ) with which at least one point of said first axisymmetrical surface ( 30 ) may be obtained, said at least one parameter (P) being a coordinate of said at least one point in a reference system associated with at least one portion of this sub-system; and a sub-step (E 26 ) for reconstructing said first axisymmetrical surface ( 30 ) from said at least one point and from said at least one constraint (CM); a step (E 60 ′) for modifying said at least one parameter (P) in said reference system for modeling said second surface ( 40 ); and a step (E 75 ) for recording said second surface ( 40 ) in a memory ( 17 ) of said computer ( 10 ).