What is "descriptive geometry"

Geometry \Ge*om"e*try\, n.; pl. Geometries[F. g['e]om['e]trie, L. geometria, fr. Gr. ?, fr. ? to measure land; ge`a, gh^, the earth + ? to measure. So called because one of its earliest and most important applications was to the measurement of the earth's surface. See Geometer.]

1. That branch of mathematics which investigates the relations, properties, and measurement of solids, surfaces, lines, and angles; the science which treats of the properties and relations of magnitudes; the science of the relations of space.

2. A treatise on this science.

   Analytical geometry, or Co["o]rdinate geometry, that branch of mathematical analysis which has for its object the analytical investigation of the relations and properties of geometrical magnitudes.

   Descriptive geometry, that part of geometry which treats of the graphic solution of all problems involving three dimensions.

   Elementary geometry, that part of geometry which treats of the simple properties of straight lines, circles, plane surface, solids bounded by plane surfaces, the sphere, the cylinder, and the right cone.

   Higher geometry, that pert of geometry which treats of those properties of straight lines, circles, etc., which are less simple in their relations, and of curves and surfaces of the second and higher degrees.

Descriptive \De*scrip"tive\, a. [L. descriptivus: cf. F. descriptif.] Tending to describe; having the quality of representing; containing description; as, a descriptive figure; a descriptive phrase; a descriptive narration; a story descriptive of the age.

Descriptive anatomy, that part of anatomy which treats of the forms and relations of parts, but not of their textures.

Descriptive geometry, that branch of geometry. which treats of the graphic solution of problems involving three dimensions, by means of projections upon auxiliary planes.
--Davies & Peck (Math. Dict. ) -- De*scrip"tive*ly, adv. -- De*scrip"tive*ness, n.

n. A graphical protocol which creates three-dimensional virtual space on a two-dimensional plane.

n. the geometry of properties that remain invariant under projection [syn: projective geometry]

Descriptive geometry is the branch of geometry which allows the representation of three-dimensional objects in two dimensions, by using a specific set of procedures. The resulting techniques are important for engineering, architecture, design and in art. The theoretical basis for descriptive geometry is provided by planar geometric projections. Gaspard Monge is usually considered the "father of descriptive geometry". He first developed his techniques to solve geometric problems in 1765 while working as a draftsman for military fortifications, and later published his findings.

Monge's protocols allow an imaginary object to be drawn in such a way that it may be 3-D modeled. All geometric aspects of the imaginary object are accounted for in true size/to-scale and shape, and can be imaged as seen from any position in space. All images are represented on a two-dimensional surface.

Descriptive geometry uses the image-creating technique of imaginary, parallel projectors emanating from an imaginary object and intersecting an imaginary plane of projection at right angles. The cumulative points of intersections create the desired image.