The following four lines of code in MapleTM produce this animation of the intersection of a plane of increasing slope with a right circular cone.
> with(plots):
> C := plot3d([z*cos(t), z*sin(t), z], t = -Pi..Pi, z = -3..5, transparency = .6):
> P := animate(plot3d, [1+x*tan(t), x = -3..5, y = -3..5], t = 0..1.57, frames=51, view = -3..5, orientation = [-135, 35]):
> display([C, P]);
(t is the angle in radians between the moving plane and the xy plane)
When the plane is parallel to the xy plane (t =0,
perpendicular to the axis of symmetry of the cone),
the intersection is a circle (eccentricity
As the slope of the plane increases, the intersection passes through ellipses of
increasing eccentricity
half way through the animation,
Thereafter,
Finally, when the plane is vertical (parallel to the axis of the cone),
the plane passes through the origin, e is infinite and the conic
section becomes a line pair.
In Maple one can control the playback speed or step frame by frame.
One can also adjust the viewing angle and other parameters within Maple.