Point at infinity complex field, the set of points at infinity is a manifold. In artistic drawing and technical perspective, the projection on the picture plane of the point at infinity of a class of parallel lines is called their vanishing point. In hyperbolic geometry, points at infinity are typically named ideal points. Unlike Euclidean and elliptic geometries, each line has two points at infinity: given a line "l" and a point "P" not on "l", the right- and left-limiting parallels converge asymptotically to different points at infinity. All points at infinity together form the Cayley absolute or boundary of a hyperbolic plane.
Radiant (meteor shower) seen from the perspective of the observer, who views a two-dimensional projection against the sky. The geometric effect is identical to crepuscular rays, where parallel sunbeams appear to converge. A meteor that does not point back to the known radiant for a given shower is known as a "sporadic" and is not considered part of that shower. Shower meteors may appear a short time before the radiant has risen in observer's eastern sky. The radiant in such cases is above the horizon at the meteor's altitude. During the active period of most showers, the radiant moves nearly one degree eastwards,