Interprete the circles as level lines of a cone
and the lines as level lines of a plane intersecting the cone
Distance Ratio: 0.8 ... 2.0
The curve is drawn so that the ratio parameter above
is the ratio of the distances
from the curve point
to the center of the circles and to the thick line
at the right. The center point is called focal point,
the line is called directrix.
If this ratio equals 1, then we have a Parabola.
If one interpretes the circles as level lines of a
cone and the lines as the level lines of a plane
such that equal colors indicate the same height,
then one recognizes the curve as the intersection of
a plane and a cone. It is a Conic
Section, and the
above construction is a property of conic sections.