Perspective (graphical) with one-point perspective. These parallel lines converge at the vanishing point. One-point perspective exists when the picture plane is parallel to two axes of a rectilinear (or Cartesian) scene – a scene which is composed entirely of linear elements that intersect only at right angles. If one axis is parallel with the picture plane, then all elements are either parallel to the picture plane (either horizontally or vertically) or perpendicular to it. All elements that are parallel to the picture plane are drawn as parallel lines. All elements that are perpendicular to the picture plane converge at a single point
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,