Difference between general shape design and automotive class a in catia

Hi all,i need a little help,i am trying to model a car in catia,and i cant solve in which part i will do it,now im thinking about automotice class a (ACA) but im not sure how it works,it have some nice 3d lines but after i finish drawing them,i cant edit them like in free style,and there is no combine option,any help?

2 Answers

Class A Surfaces (Icem Shape, Automotive class a) is used for all visivle surface. These surfaces have to be C0 (point) C1 (tangent) and C2 (curvature) continues.
GSD is used for the body in white (non visible surfaces, structure) GSD is "mostly" only C0 and C1 continues.

best regards

general shape design is a workbench in Catia. where as A class surface is the term used in plastic product Design.