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)
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(2)
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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.