# What is Class A surfacing and how to determine that a surface belongs to this class?

What is Class A surfacing and how to determine that a surface belongs to this class?

Class A surfaces are used in the automotive industrie (maybe in other too). All visible surface of a car MUST be class A. It describes the quality, how two surfaces fit together. Like Sudhir said, there are different levels:
G0 (point continuity): "no holes between the surfaces"
G1 (tangent continuity): "you can´t feel an edge between the surfaces"
G2 (curvature continuity): "in the paintwork, you ca´t see a transition"
G3 (I don´t know the name): "the transition of the curvature is smooth"
Class A means at least G0, G1 and G2 between ALL surfaces.
In the free style shaper are different tools to analyse the connection of the surfaces. Some more hints are here:

greetings

I remember something like from the Lecture's at college. it is more like the continuity of surfaces, by tangency or curvatures for better surfacing in automobile surfacing.

Class A surfaces having different meaning for different industry, as every industry has different parameters and definitions for class A surface.
But in common we can define Class A Surfaces as the surfaces which fulfill the requirements of designer as well as of an engineer, that mean it should be meeting aesthetic requirement of part as well as should meet engineering requirement of that part. Only aesthetic look does not make it class A surface.
If we talk about continuity between surfaces in class A, not necessary to be G2 or G3 always, It could be G1. It depending on highlights flow required on that area. Especially at blend or filleted areas.

G3 Continuity Comb with single span 5 cv maximum 7 cv surface or curve. Class A modeling is a little hard but the continuity between curves to start with must be G3 Curvature meaning the curvature comb must be smooth you can also achieve higher degree of curvature such as G4 G5 G6 but class A requires at minimum G3 Continuity between surfaces.

In the automotive industry Class A surfaces are those that can be always seen by the customer, such as the body side or the console. The Class B surfaces are the ones seen by the customer when a door or gate is opened, such as the seal flange of the doors, and the Class C surfaces are the ones not seen by the customer, for instance inner brackets or the b-side features of the plastic parts.

kindly send me a class A surface in .step or .iges