Foreshortening

Linear or point-projection perspective (from la, perspicere 'to see through') is one of two types of graphical projection perspective in the graphic arts; the other is parallel projection. Linear perspective is an approximate representation, generally on a flat surface, of an image as it is seen by the eye. Perspective drawing is useful for representing a three-dimensional scene in a two-dimensional medium, like paper.

The most characteristic features of linear perspective are that objects appear smaller as their distance from the observer increases, and that they are subject to ''foreshortening'', meaning that an object's dimensions along the line of sight appear shorter than its dimensions across the line of sight. All objects will recede to points in the distance, usually along the horizon line, but also above and below the horizon line depending on the view used.

Italian Renaissance painters and architects including Masaccio, Paolo Uccello, Piero della Francesca and Luca Pacioli studied linear perspective, wrote treatises on it, and incorporated it into their artworks.

Overview

Perspective works by representing the light that passes from a scene through an imaginary rectangle (the picture plane), to the viewer's eye, as if a viewer were looking through a window and painting what is seen directly onto the windowpane. If viewed from the same spot as the windowpane was painted, the painted image would be identical to what was seen through the unpainted window. Each painted object in the scene is thus a flat, scaled down version of the object on the other side of the window.

One-point perspective

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Two-point perspective

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Three-point perspective

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Curvilinear perspective

Additionally, a central vanishing point can be used (just as with one-point perspective) to indicate frontal (foreshortened) depth.

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History

Early history

The earliest art paintings and drawings typically sized many objects and characters hierarchically according to their spiritual or thematic importance, not their distance from the viewer, and did not use foreshortening. The most important figures are often shown as the highest in a composition, also from hieratic motives, leading to the so-called "vertical perspective", common in the art of Ancient Egypt, where a group of "nearer" figures are shown below the larger figure or figures; simple overlapping was also employed to relate distance. Additionally, oblique foreshortening of round elements like shields and wheels is evident in Ancient Greek red-figure pottery.

Systematic attempts to evolve a system of perspective are usually considered to have begun around the fifth century BC in the art of ancient Greece, as part of a developing interest in illusionism allied to theatrical scenery. This was detailed within Aristotle's ''Poetics'' as ''skenographia'': using flat panels on a stage to give the illusion of depth. The philosophers Anaxagoras and Democritus worked out geometric theories of perspective for use with ''skenographia''. Alcibiades had paintings in his house designed using ''skenographia'', so this art was not confined merely to the stage. Euclid in his ''Optics'' () argues correctly that the perceived size of an object is not related to its distance from the eye by a simple proportion. In the first-century BC frescoes of the Villa of P. Fannius Synistor, multiple vanishing points are used in a systematic but not fully consistent manner.

Chinese artists made use of oblique projection from the first or second century until the 18th century. It is not certain how they came to use the technique; Dubery and Willats (1983) speculate that the Chinese acquired the technique from India, which acquired it from Ancient Rome, while others credit it as an indigenous invention of Ancient China. Oblique projection is also seen in Japanese art, such as in the Ukiyo-e paintings of Torii Kiyonaga (1752–1815).

By the later periods of antiquity, artists, especially those in less popular traditions, were well aware that distant objects could be shown smaller than those close at hand for increased realism, but whether this convention was actually used in a work depended on many factors. Some of the paintings found in the ruins of Pompeii show a remarkable realism and perspective for their time. It has been claimed that comprehensive systems of perspective were evolved in antiquity, but most scholars do not accept this. Hardly any of the many works where such a system would have been used have survived. A passage in Philostratus suggests that classical artists and theorists thought in terms of "circles" at equal distance from the viewer, like a classical semi-circular theatre seen from the stage. The roof beams in rooms in the Vatican Virgil, from about 400 AD, are shown converging, more or less, on a common vanishing point, but this is not systematically related to the rest of the composition.

Medieval artists in Europe, like those in the Islamic world and China, were aware of the general principle of varying the relative size of elements according to distance, but even more than classical art were perfectly ready to override it for other reasons. Buildings were often shown obliquely according to a particular convention. The use and sophistication of attempts to convey distance increased steadily during the period, but without a basis in a systematic theory. Byzantine art was also aware of these principles, but also used the reverse perspective convention for the setting of principal figures. Ambrogio Lorenzetti painted a floor with convergent lines in his ''Presentation at the Temple'' (1342), though the rest of the painting lacks perspective elements.

Renaissance

It is generally accepted that Filippo Brunelleschi conducted a series of experiments between 1415 and 1420, which included making drawings of various Florentine buildings in correct perspective. According to Vasari and Antonio Manetti, in about 1420, Brunelleschi demonstrated his discovery by having people look through a hole in the back of a painting he had made. Through it, they would see a building such as the Florence Baptistery. When Brunelleschi lifted a mirror in front of the viewer, it reflected his painting of the buildings which had been seen previously, so that the vanishing point was centered from the perspective of the participant. Brunelleschi applied the new system of perspective to his paintings around 1425.

This scenario is indicative, but faces several problems.
First of all, nothing can be said for certain about the perspective of the baptistery of San Giovanni, because Brunelleschi's panel is lost.
Second, no other perspective painting by Brunelleschi is known.
Third, in the account written by Antonio di Tuccio Manetti at the end of the 15th century on Brunelleschi's panel, there is not a single occurrence of the word experiment.
Fourth, the conditions listed by Antonio di Tuccio Manetti are contradictory with each other. For example, the description of the eyepiece sets a visual field of 15° much narrower than the visual field resulting from the urban landscape described.

This scenario is still debated, however, because Brunelleschi's tavoletta is lost, which does not allow a direct assessment of the correctness of his perspective construction, and because the conditions listed by Antonio di Tuccio Manetti in his ''Vita di Ser Brunellesco'' are inconsistent.

Soon after Brunelleschi's demonstrations, nearly every artist in Florence and in Italy used geometrical perspective in their paintings and sculpture, notably Donatello, Masaccio, Lorenzo Ghiberti, Masolino da Panicale, Paolo Uccello, and Filippo Lippi. Not only was perspective a way of showing depth, it was also a new method of creating a composition. Visual art could now depict a single, unified scene, rather than a combination of several. Early examples include Masolino's ''St. Peter Healing a Cripple and the Raising of Tabitha'' (), Donatello's ''The Feast of Herod'' (), as well as Ghiberti's '' Jacob and Esau'' and other panels from the east doors of the Florence Baptistery. Masaccio (d. 1428) achieved an illusionistic effect by placing the vanishing point at the viewer's eye level in his ''Holy Trinity'' (), and in '' The Tribute Money'', it is placed behind the face of Jesus. In the late 15th century, Melozzo da Forlì first applied the technique of foreshortening (in Rome, Loreto, Forlì and others).

This overall story is based on qualitative judgments, and would need to be faced against the material evaluations that have been conducted on Renaissance perspective paintings.
Apart from the paintings of Piero della Francesca, which are a model of the genre, the majority of 15th century works show serious errors in their geometric construction. This is true of Masaccio's ''Trinity'' fresco and of many works, including those by renowned artists like Leonardo da Vinci.

As shown by the quick proliferation of accurate perspective paintings in Florence, Brunelleschi likely understood (with help from his friend the mathematician Toscanelli), but did not publish, the mathematics behind perspective. Decades later, his friend Leon Battista Alberti wrote ' (), a treatise on proper methods of showing distance in painting. Alberti's primary breakthrough was not to show the mathematics in terms of conical projections, as it actually appears to the eye. Instead, he formulated the theory based on planar projections, or how the rays of light, passing from the viewer's eye to the landscape, would strike the picture plane (the painting). He was then able to calculate the apparent height of a distant object using two similar triangles. The mathematics behind similar triangles is relatively simple, having been long ago formulated by Euclid. Alberti was also trained in the science of optics through the school of Padua and under the influence of Biagio Pelacani da Parma who studied Alhazen's ''Book of Optics''. This book, translated around 1200 into Latin, had laid the mathematical foundation for perspective in Europe.

Piero della Francesca elaborated on ''De pictura'' in his '' De Prospectiva pingendi'' in the 1470s, making many references to Euclid. Alberti had limited himself to figures on the ground plane and giving an overall basis for perspective. Della Francesca fleshed it out, explicitly covering solids in any area of the picture plane. Della Francesca also started the now common practice of using illustrated figures to explain the mathematical concepts, making his treatise easier to understand than Alberti's. Della Francesca was also the first to accurately draw the Platonic solids as they would appear in perspective. Luca Pacioli's 1509 ''Divina proportione'' (''Divine Proportion''), illustrated by Leonardo da Vinci, summarizes the use of perspective in painting, including much of Della Francesca's treatise. Leonardo applied one-point perspective as well as shallow focus to some of his works.

Two-point perspective was demonstrated as early as 1525 by Albrecht Dürer, who studied perspective by reading Piero and Pacioli's works, in his ''Unterweisung der messung'' ("Instruction of the measurement").

Limitations

Perspective images are calculated assuming a particular vanishing point. In order for the resulting image to appear identical to the original scene, a viewer of the perspective must view the image from the exact vantage point used in the calculations relative to the image. This cancels out what would appear to be distortions in the image when viewed from a different point. These apparent distortions are more pronounced away from the center of the image as the angle between a projected ray (from the scene to the eye) becomes more acute relative to the picture plane. In practice, unless the viewer chooses an extreme angle, like looking at it from the bottom corner of the window, the perspective normally looks more or less correct. This is referred to as "Zeeman's Paradox". It has been suggested that a drawing in perspective still seems to be in perspective at other spots because we still perceive it as a drawing, because it lacks depth of field cues."...the paradox is purely conceptual: it assumes we view a perspective representation as a retinal simulation, when in fact we view it as a two dimensional painting. In other words, perspective constructions create visual symbols, not visual illusions. The key is that paintings lack the depth of field cues created by binocular vision; we are always aware a painting is flat rather than deep. And that is how our mind interprets it, adjusting our understanding of the painting to compensate for our position."
Retrieved on 25 December 2006

See also

* Anamorphosis
* Camera angle
* Cutaway drawing
* Perspective control
* Perspective-taking
* Trompe-l'œil
* Uki-e
* Zograscope

Notes

References

Sources

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Further reading

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External links

A tutorial covering many examples of linear perspective

Teaching Perspective in Art and Mathematics through Leonardo da Vinci's Work
at Mathematical Association of America

Metaphysical Perspective in Ancient Roman-Wall Painting


How to Draw a Two Point Perspective Grid
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Creating Comics

{{DEFAULTSORT:Perspective (Graphical)
Perspective projection
Technical drawing
Functions and mappings
Composition in visual art
Italian inventions