 Orthographic projection

Part of a series on: Graphical projection  Parallel projection
 Orthographic projection
 Multiviews
 Plan, or floor plan
 Section
 Elevation
 Auxiliary
 Axonometric projection (i.e. pictorials)
 Isometric projection
 Dimetric projection
 Trimetric projection
 Multiviews
 Oblique projection
 Cavalier projection
 Cabinet projection
 Orthographic projection
 Perspective projection
 Linear perspective
 Onepoint perspective
 Twopoint perspective
 Threepoint perspective
 Zeropoint perspective
 Curvilinear perspective
 Reverse perspective
 Linear perspective
Views Bird'seye view/Aerial view
 Detail view
 3/4 perspective
 Cutaway drawing
 Exploded view drawing
 Fisheye
 Fixed 3D
 Panorama
 Topdown perspective
 Worm'seye view
 Zoom
Orthographic projection (or orthogonal projection) is a means of representing a threedimensional object in two dimensions. It is a form of parallel projection, where all the projection lines are orthogonal to the projection plane,^{[1]} resulting in every plane of the scene appearing in affine transformation on the viewing surface. It is further divided into multiview orthographic projections and axonometric projections. A lens providing an orthographic projection is known as an (objectspace) telecentric lens.
The term orthographic is also sometimes reserved specifically for depictions of objects where the axis or plane of the object is also parallel with the projection plane,^{[1]} as in multiview orthographic projections.
Contents
Origin
The orthographic projection has been known since antiquity, with its cartographic uses being well documented. Hipparchus used the projection in the 2nd century B.C. to determine the places of starrise and starset. In about 14 B.C., Roman engineer Marcus Vitruvius Pollio used the projection to construct sundials and to compute sun positions.^{[2]}
Vitruvius also seems to have devised the term orthographic (from the Greek orthos (= “straight”) and graphē (= “drawing”) for the projection. However, the name analemma, which also meant a sundial showing latitude and longitude, was the common name until François d'Aguilon of Antwerp promoted its present name in 1613.^{[2]}
The earliest surviving maps on the projection appear as woodcut drawings of terrestrial globes of 1509 (anonymous), 1533 and 1551 (Johannes Schöner), and 1524 and 1551 (Apian).^{[2]}
Multiview orthographic projections
Main article: Multiview orthographic projectionWith multiview orthographic projections, up to six pictures of an object are produced, with each projection plane parallel to one of the coordinate axes of the object. The views are positioned relative to each other according to either of two schemes: firstangle or thirdangle projection. In each, the appearances of views may be thought of as being projected onto planes that form a 6sided box around the object. Although six different sides can be drawn, usually three views of a drawing give enough information to make a 3D object. These views are known as front view, top view and right side view.
Pictorials
Main article: Axonometric projectionWithin orthographic projection there is the subcategory known as pictorials. Axonometric pictorials show an image of an object as viewed from a skew direction in order to reveal all three directions (axes) of space in a single picture.^{[3]} Orthographic pictorial instrument drawings are often used to approximate graphical perspective projections, but there is attendant distortion in the approximation. Because pictorial projections inherently have this distortion, in the instrument drawing of pictorials, great liberties may then be taken for economy of effort and best effect. Orthographic pictorials rely on the technique of axonometric projection ("to measure along axes").
See also
References
 ^ ^{a} ^{b} Maynard, Patric (2005). Drawing distinctions: the varieties of graphic expression. Cornell University Press. pp. 22. ISBN 0801472806. http://books.google.com/?id=4Y_YqOlXoxMC&pg=PA22&lpg=PA22&dq=axonometric+orthographic&q=axonometric%20orthographic.
 ^ ^{a} ^{b} ^{c} Snyder, John P. (1993). Flattening the Earth: Two Thousand Years of Map Projections pp. 16–18. Chicago and London: The University of Chicago Press. ISBN 0226767469.
 ^ Mitchell, William; Malcolm McCullough (1994). Digital design media. John Wiley and Sons. pp. 169. ISBN 0471286664. http://books.google.com/?id=JrZoGgQEhKkC&pg=PA169&dq=axonometric+orthographic#v=onepage&q=axonometric%20orthographic.
External links
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