Perspective- a technique of depicting volumes and spatial relationships on a flat surface.
Linear Perspective - a mathematical system for representing three-dimensional objects and space on a two-dimensional surface by means of intersecting lines that are drawn vertically and horizontally and that radiate from one point(one-point perspective),two points (two-point perspective), or several points on a horizon line as perceived by a viewer imagined in an arbitrarily fixed position.
Atmospheric Perspective (or Aerial Perspective)- a technique of rendering depth or distance in painting or drawing by modifying the tone or hue and distinctness of objects perceived as receding from the picture plane, esp. by reducing distinctive local colors and contrasts of light and dark to a uniform light bluish-gray color.
Picture Plane- An imaginary "pane of glass" at which the viewers gaze meets the illusion created on the two dimensional surface. To extend the analogy, the viewer would trace on this glass the three- dimensional object. Not just the material surface, a concept.
Horizon Line- A level horizontal line located at eye level.
Vanishing Point- A point of convergence of parallel lines located on the Horizon Line.
Scale- The apparent size of an object.
This example illustrates the same object in relationship to the Horizon Line (Above and Below.) Notice whether you can see the top of the cube or the bottom, which way the diagonal lines slope to the vanishing point.
The following Four examples were taken from Basic Perspective Drawing- John Montague.
This example illustrates the top of a cylinder (circle) as it approaches the Horizon Line. Notice how it changes to an elipse and further squeezes to a line.
