Perspective (graphical)
Image perspective studies the means by which the illusion of three dimensional space is achieved on a two dimensional plane.
Within the category of image perspective lies a subset of images in the manner that a fine artist might produce - in which the production of a three dimensional illusion is completely intuitive according to the artistÂ’s knowledge and talents.
In addition to the artistÂ’s intuitive perspective there is a category of graphical images which are produced by the phenomenon of projection. Graphical projection uses a precision greater that the freehand abilities of a fine artist and is executed with drafting instruments on a two dimensional plane.
Graphical projection
Under Graphical projection there are three broad categories: Orthographic, Oblique, and Perspective. Orthographic Projection is derived from the principles of descriptive geometry and may produce an image of a specified, imaginary object as viewed from any direction of space. Within Orthographic projection there is an ancillary category called Pictorials. Pictorials show an image of an object as viewed from a skew direction in order to reveal all three directions of space in one picture. This is a rather trivial use of Orthographic Projection because it is ancillary to its powerful Descriptive Geometry capabilities.
Orthographic Pictorials use a technique called Axonometric ("to measure along axes") Projection. There are three categories of Pictorials within Axonometric Projection: Isometric, Diametric and Trimetric. In Isometric Pictorials, the direction of viewing is such that the three directions (axes) of space are equally foreshortened, of which the scale of foreshortening is universally known (and in many cases a full-size scale, i.e., without factoring in any foreshortening, is used to good advantage because the resultant distortion is difficult to perceive). In Dimetric Pictorials the direction of viewing is such that two of the three axes of space are equally foreshortened the scale of which must be determined according to the angle of viewing and the scale of the third direction must be determined separately. In Trimetric Pictorials, the direction of viewing is such that each of the three axes of space is unequally foreshortened. The scale along each of the three axes must be determined separately according to the angle of viewing.
Oblique Projection is used exclusively for Pictorial purposes - but in a highly distorted way. In Oblique Projections the foreshortening factors (scale) along the axes, especially along the receding axis, are completely arbitrary.
In Orthographic and Oblique Projection parallel lines in space appear parallel on the final image.
Classical Perspective Projection is seldom technically regarded as a Pictorial. Classical Perspective Projection is an attempt to exactly reproduce the image beheld by the eye, i.e., parallel lines appear to intersect. (It should be parenthetically acknowledged that the eye itself produces an inherit distortion of nature. In nature parallel lines never intersect; in the image beheld by the eye parallel lines always intersect - as in the image of receding railroad tracks). Be aware that Classical Perspective Projection produces inherent distortion of the (distorted, per parenthetical note above) image beheld by the eye - see Perspective Distortion, Source.)
Perspective in icons
Traditionally, development of various types of perspective is studied through the analysis of icons.
In most modern drawings/paintings the linear perspective is used: the further the objects are from the viewer, the smaller they are drawn and the closer they are positioned to the so-called vanishing point or points, so that the (drawing of the) most remote objects completely disappear in the vicinity of these points.
Under the linear perspective the vanishing point or points are usually placed inside the painting with the illusion that it is "beyond" the drawing.
Under the reversed perspective, or inverse perspective, or Byzantine perspective the further the objects, the larger they are drawn. (The latter name is because thes kind of perspective is observed in earlier Byzantine and Russian Orthodox icons.) Technically, the vanishing points are placed outside the painting with the illusion that they are "in front of" the painting.
It is difficult to say now what were the intentions of the ancient iconographers, but a common interpretation is that the point of perspective is on the viewer, hence The Almighty looks upon him, rather than the viewer looks upon The Almighty.
Axonometric perspective is in between the two others: the relative sizes of depicted objects do not depend on the distance to the actual ones.
See also: Perspective distortion, Perspective transform, Desargues' theorem, Perspective Distortion, Source
Referenced By
Aesthetic | Aesthetician | Aesthetics | Esthetics | Graphical method | Inverse | List of graphical methods | Perspective
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