About Default and Smart Connections
Default surface connections are established during surface creation. If the cross-boundary curves have tangent connections to an existing neighbor surface, then a surface tangent connection is established. Cross-boundary curves with a curvature connection to a neighbor surface generate an automatic Tangent connection. If the boundary curve is planar and the cross-boundary curves are normal to the same plane, then a Normal connection is created.
When you create or connect surfaces, you can also use smart surface connections to establish the following connection types:
G1 - Surface Tangent
G2 - Surface Curvature
G3 - Surface Acceleration
Draft Tangent
If you select a connection that is not supported by the cross-boundary curves, you can accept automatic curve edits that modify the curve tangent connections to establish the same tangent continuity with the neighboring surface. The required surface connection is established between the surfaces.
To create a smart connection, all of the cross-boundary curves must be Style curves in the same Style feature. They must be adjacent to the neighboring surface.