Conic Section as Bézier Curve

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Any conic section can be represented as a rational Bézier curve of degree two defined by , where
are the Bernstein polynomials and
the control points. It is always possible to write the expression in a standard form such that
. From such a form it is easy to determine the type of the conic section: if
, it is a hyperbola; if
, it is a parabola; and if
, it is an ellipse.
Contributed by: Isabelle Cattiaux-Huillard and Gudrun Albrecht (March 2011)
Open content licensed under CC BY-NC-SA
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We show how to obtain the standard form (i.e., to make the first and last weights equal to 1) of a rational Bézier curve of degree
. Let
be defined by
, where
are the Bernstein polynomials. We neither change the curve nor its degree by applying a rational linear transformation
, yielding
.
The curve is thus represented in standard form by the original control points and the new weights
by choosing
.
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