Editing Orthographic projection (section)

== Types ==
{{comparison_of_graphical_projections.svg}}

Three sub-types of orthographic projection are ''[[isometric projection]]'', ''dimetric projection'', and ''trimetric projection'', depending on the exact angle at which the view deviates from the orthogonal.<ref name="maynard"/><ref name="mcreynolds">{{Cite book | last = McReynolds | first = Tom |author2= David Blythe | title = Advanced graphics programming using openGL | publisher = Elsevier | year = 2005 | pages = 502 | url = https://books.google.com/books?id=bmv2HRpG1bUC&q=axonometric | isbn = 1-55860-659-9}}</ref> Typically in axonometric drawing, as in other types of pictorials, one axis of space is shown to be vertical.

In '''isometric projection''', the most commonly used form of axonometric projection in engineering drawing,<ref name="godse">{{Cite book | title = Computer graphics | publisher = Technical Publications | year = 1984 | pages = 29 | url = https://books.google.com/books?id=YkVp-2ZrmyMC&q=axonometric+orthographic&pg=PT224 | isbn = 81-8431-558-9 | last = Godse | first = Atul P.}}</ref> the direction of viewing is such that the three axes of space appear equally [[Perspective (graphical)#Foreshortening|foreshortened]], and there is a common angle of 120° between them.  As the distortion caused by foreshortening is uniform, the proportionality between lengths is preserved, and the axes share a common scale; this eases one's ability to take measurements directly from the drawing.  Another advantage is that 120° angles are easily constructed using only a [[Compass and straightedge constructions|compass and straightedge]].

In '''dimetric projection''', the direction of viewing is such that two of the three axes of space appear equally foreshortened, of which the attendant scale and angles of presentation are determined according to the angle of viewing; the scale of the third direction is determined separately.

In '''trimetric projection''', the direction of viewing is such that all of the three axes of space appear unequally foreshortened. The scale along each of the three axes and the angles among them are determined separately as dictated by the angle of viewing. Trimetric perspective is seldom used in technical drawings.<ref name="mcreynolds"/>