Drawing Conic Curves
Circles are special cases of a class of curves known as conics. Conics are distingished by second-degree descriminating functions
of the form:
Note: Equation 3-50 (pg. 110) is wrong in the book!
(Actually it is just inconsistent with equation 3-51).
The values of the constants, A, B, C, D, E, and F determines the type
of curve as follows:
To make things confusing, mathematicians often refer to the term B2 - 4AC
as the conic discriminant. Here we will stick to the computer graphics definition of a discriminant
as a function that partitions interior and exterior half-spaces.
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