File:A manual of elementary geometrical drawing, involving three dimensions. Designed for use in high schools, academies, engineering schools, etc. - and for the self-instruction of inventors,artizans, (14579367727).jpg

Identifier: manualofelementa01warr (find matches)
Title: A manual of elementary geometrical drawing, involving three dimensions. Designed for use in high schools, academies, engineering schools, etc. : and for the self-instruction of inventors,artizans, etc. ... In five divisions ..
Year: 1867 (1860s)
Authors: Warren, S. Edward (Samuel Edward), 1831-1909
Subjects: Geometrical drawing Mechanical drawing
Publisher: New York : J. Wiley and son
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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Text Appearing Before Image:
abinet projection, all these diagonals show aslines, and, except BE, separately from the edges of the cube. 5. Having thus shown something of what cabinet projection is,let us proceed to learn how it is formed. Simialy rememberingthat a line, as AB, Fig. 3, which makes angles of 45° with lines, as .A Kg. 3. AC and BC, which are perpendicular to each other, cuts off equaldistances, CA and CB, from their intersection, C; it is evidentthat the eye is, in reference to Fig. 2, at an infinite distance fromthe paper, and above and to the right of the object, in a plane j)er-pendicular to the paper in the line EB, and tliat the direction ofvision makes an angle of 45° with the paper, taken as the plane ofprojection. Thus EH—ED, and is the cabinet projection of the edge whichis really perpendicular to the paper at E, and has the point E forits vertical projection. 6. We have thus a system of projections which differ from allthose already noticed, in that the projecting lines are oblique to
Text Appearing After Image:
TKeM^DtAKiu(ivEnBMritSLilh.ra44gi1roalwayNY. CABINET PKOJECTIONS. 91 the plane of projection. Such are true oblique projections ; thoughbodies placed obliquely to the planes of projection are sometimessaid to be shown in oblique projection. But in truth they are onlyseen obliquely, while they are projected perpendicularly, that is byprojecting lines which are perpendicular to the planes of projec-tion. The two systems of projection, in which the eye is at an infinitedistance, are, therefore, perpendicular projection., in which theprojecting lines are perpendicular to the planes of projection; andoblique projection., in which they are oblique to those planes. Isometrical projection is thus seen to be a variety oi XxvlQ perpen-dicular projection., in which the object is, however, seen obliquely,and in which each plane side of a solid right angle is, indeed,viewed with equal obliquity. Cabinet projection is a species of oblique projection. v. Lines making angles of 45° with the vertical

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