Vanishing point of multipoint perspective, and historian Kirsti Andersen compiled these observations. She notes, in terms of projective geometry, the vanishing point is the image of the point at infinity associated with , as the sightline from through the vanishing point is parallel to . As a vanishing point originates in a line, so a vanishing line originates in a plane that is not parallel to the picture . Given the eye point , and the plane parallel to and lying on , then the vanishing line of is . For example, when is the ground plane and is the horizon plane,
Point-to-point transit Point-to-point transit Point-to-point transit refers to a transportation system in which a plane, bus, or train travels directly to a destination, rather than going through a central hub. This differs from the spoke-hub distribution paradigm in which the transportation goes to a central location where passengers change to another train, bus, or plane to reach their destination. The point-to-point model is used widely by low cost carriers, including Allegiant Air and Southwest Airlines in the U.S., and European carriers such as Ryanair, easyJet and Wizzair. Many such airlines sell each flight leg independently and have no concept of round-trip ticketing