Parallel curves, frequently called "offset curves" in computer graphics applications, are curves which are displaced from a base curve by a constant offset,
either positive or negative, in the direction of the curve's normal. The two branches
of the parallel curve a distance 
away from a parametrically represented base curve 
are
 |  |  |
(1)
|
 |  |  |
(2)
|
where 
and 
.
The above figure shows curves parallel to a circle, ellipse, and 3-petalled rose curve,
where the base curves are indicated in red.
