A Manual of Elementary Projection Drawing, Involving Three Dimensions

A Manual of Elementary Projection Drawing, Involving Three Dimensions

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1872 edition. Excerpt: ...I..--Facts, Principles, and Preliminary Problems. 158. Rays of light are here assumed to proceed in parallel straight lines. Sensibly they do thus proceed from a source as distant as the sun, as is shown by the fact that the shadows of parallel straight lines upon plane surfaces are straight and parallel; or that we cannot see through a bent tube. One can learn by simple inspection, from the shadows on buildings, many facts about shadows, which follow directly from the preceding principle, and which point out the solution of those simple problems, in which the shadows are, cast by straight lines upon planes. 159. It will be thus observed that the shadow of a vertical edge ab, PL VIIL, Fig. 78, of the body of the house will be a vertical line, a'b', on the front wall of the wing behind it; that the shadow of a horizontal line, as be--the arm for a swinging sign--which is parallel to the wing wall, will be a horizontal line, 5V, parallel to be; that a horizontal line, be, which is perpendicular to the wing wall, will have an oblique shadow, cb', on that wall, commencing at c, where the line pierces the wing wall, and ending at Z', where a ray of light through b pierces the wing wall; and finally that the shadow of & point, b, is at V where the ray bb', through that point, pierces the surface receiving the shadow. 160. Passing now to PI. VIIL, Fig. 79, which represents a chimney upon a flat roof, we observe that the shadows of bo and cd--lines parallel to the roof--are b'cf and c'd', lines equal to, and parallel to, the lines be and cd; and that the shadows of ab and ed are aV and ed'--similar to the shadow cV in Fig. 1&--i. e. commencing at a and e where the lines casting them meet the roof, and ending at #' and d where rays through b and, ...show more

Product details

  • Paperback | 50 pages
  • 189 x 246 x 3mm | 109g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236668596
  • 9781236668592