A hyperbolic paraboloid composed of straight line segments. Parabolic sections in xz and yz
planes through the curving surface are shown in white, some opening upward, some
downward. It can be seen that this is a doubly ruled surface, with 2 straight lines lying in the
surface intersecting at every point on the surface. The 2 yellow lines that meet at the center
can be seen as asymptotes. Sections through the surface in horizontal (xy) planes are
hyperbolas, though none are delineated.