Cyclopedia of Drawing Volume 2; A General Reference Work on Drawing and Allied Subjects for Architects, Mechanical Engineers, Etc - Softcover
Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 Excerpt: ...point bv is more distant than the point av. Therefore, b„ which shows the true measurement for the point bv, must be laid off to the riyht of a?. 104. It sometimes happens that a line extends in front of the picture plane, as has already been seen in the lines of the nearest corner of the porch in Fig. 22. It may be desired to extend the line avdv in Fig. 27, in front of the picture plane, to the point y, as-indicated in the perspective projection. In this case, the point ap being more distant than the point yv, and m"1 being to the right of SPV, the true measurement of avyv must be laid off on VII, in such a manner that the measurement for av will be to the left of the measurement for yv. In other words, y, must be on VH, to the right of the distance avyl showing the true length of «ryv. Note.--The true length of any line which extends in front of the picture plane will be shorter than the perspective of the line. 105. IIaving determined the lierspective of any line, as (/1V, its true length may be determined by drawing measure lines through d? and cv. The distance intercepted on VII, by these measure lines will show the true length of the line. Thus, dvcv vanishes at yab. Its measure punt must therefore be »«ab. Two lines drawn from 7«ab, and passing through cvand d? respectively, will intersect VlI,in the points and d.,. The distance between and d2 is the true length of cvdv. This distance will be found equal to opi,, which is the true measure for the opposite and equal side (arip) of the rectangle. In a similar manner, the true length of bl'ev may be found by drawing measure lines from 7nnA through br and cv respectively, b e will show the true length of cvbv, and should be equal to afd, which is the true length of the opp...
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