According to the theory of quadric surface, it is known that the odd direction of quadric surface is geometrically parallel to any radial surface of quadric surface, and the non-forward direction of quadric surface refers to the straight line that educates two points with quadric surface, so the odd direction is not the non-forward direction of quadric surface.

Generally speaking, a straight line intersects a quadric surface at two points. If it intersects with more than three points, then all the lines are on the surface. This line is called the generatrix of the surface. If a quadric surface is cut by a parallel plane, then its section line is a quadric curve.