转自:Rhino help topics

Positional Continuity (G0)
G0 continuity means that the end points of a curve or the edges of two surfaces touch each other. End control points are at the same location.


Tangent Continuity (G1)
G1 continuity means that the tangent direction of the two curves or surfaces is the same. Fillet arcs form this kind of continuity with the lines or surfaces filleted. The two control points of the arc and the adjacent curve line up.
Curves and surfaces with G1 continuity are also G0 continuous.


Curvature Continuity (G2)
G2 continuity means that the tangent direction and the curvature of the two curves or surfaces is the same. Blend, BlendSrf, Match, and MatchSrf form this kind of continuity. Three control points of the blend and the adjacent curve line up (up to degree 3 curves).
Curves and surfaces with G2 continuity are also G1 and therefore G0 continuous.