Definition for a conic.

If the subtype is an ellipse then it is counterclockwise when viewed in the
direction opposite the Z axis of the matrix. The parameters meet the same
requirements as for an arc. The major axis is parallel to the X axis of the
matrix, and the minor axis is parallel to the Y axis. Conic_type is
UF_conic_ellipse_subtype. K1 is the semimajor axis, and k2 is the semiminor
axis.

If the subtype is a parabola, then the X axis of the matrix is the direction
of the centerline of a parabola, which opens out along that direction. The
start and end angles may be any real numbers, as long as start_angle is less
than end_angle. Conic type is UF_conic_parabola_subtype.

If the subtype is a hyperbola, then the X axis of the matrix is the direction
of the centerline of the hyperbola, which opens out along that direction. The
start and end angles must be in the interval (-pi/2, +pi/2). Note that the
hyperbola is numerically unstable at values close to the endpoints of this
interval. Conic_type is UF_conic_hyperbola_subtype.