The one-sided outer edges of a surface feature are
displayed in cerise [pink].
Continuity between surface patches is important for both aesthetic and functional reasons. Poor continuity can show creases and show each individual patch's boundaries. Continuity between curves and surfaces can be expressed as geometric (G0, G1, G2) continuity.
Click image to enlarge
G0 Continuity: Positional continuity. Two curves that share an endpoint, two surfaces that share a boundary are G0 continuous.
G1 Continuity: Tangential continuity. Two curves that share an endpoint, two surfaces that share a boundary are G1 continuous when the normals at the join/boundary are exactly aligned in direction - at that point they are travelling in the same direction.
G2 Continuity: Curvature continuity. Two curves that share an endpoint, two surfaces that share a boundary are G2 continuous when they have the same curvature values where they meet.
If your model is symmetrical then it will generally be quicker and more robust to model half of it and then mirror the whole model - at least to the point where it becomes asymmetrical.
To achieve continuity across the midplane:
All curves and resultant surfaces must be normal to the midplane.
Surfaces within a model are often classified according to their aesthetic importance in the final product.
The fundamental outer surfaces which are most prominent in a product are often classed as the A surfaces - those which need most aesthetic consideration, ie. the top surfaces of the mouse in your hand.
The surfaces which are generally hidden but may still be seen by the user, ie. the bottom of the mouse, are classed as the B surfaces.
The C surfaces are then the internal, always hidden surfaces which need no
|Loughborough Design School. © Sean Kerslake 2011|