Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . be required to prepare in writing theexact description and data for additional exercises, and then work them out, is very important,for it is a good test of the students grasp of the subject so far as the ground has been covered,and his powers of concentration. SHADOWS OF SOLIDS AND OF GROUPS OF SOLIDS 35 SHADOWS OF SOLIDS AND OF GROUPS OF SOLIDS Section 12. The more difficult cases of shadow problems, involving the useof solids, may now be undertaken. Let the rays of light be
Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . be required to prepare in writing theexact description and data for additional exercises, and then work them out, is very important,for it is a good test of the students grasp of the subject so far as the ground has been covered,and his powers of concentration. SHADOWS OF SOLIDS AND OF GROUPS OF SOLIDS 35 SHADOWS OF SOLIDS AND OF GROUPS OF SOLIDS Section 12. The more difficult cases of shadow problems, involving the useof solids, may now be undertaken. Let the rays of light be parallel as previously,and directed toward the planes of projection, the direction to be shown b)- theplan and elevation of an arrow line. Before commencing to work out the solutions for such shadow problemsas now to be dealt with, the student must endeavor to picture or imagine the solidor group represented by the plan and elevation, or described verbally, with thelight directed toward it, and then try to decide what edges will cause or are likelyto cause the outline or contour of the shadow which will be Fig. 35- The student will not be able to make very satisfactory progress until he canreadily conceive mental pictures of what he has to deal with, realizing the relationof what he is picturing to the vertical and horizontal planes of projection, andjudging what the projections and other results might be like. Therefore it isimportant that the student should take advantage of every opportunity whichpresents itself to train himself in these matters. In Fig. 35 it will be seen that a cube is represented, and by studying it assuggested above, it will be concluded that the light will fall on three of its faces,and that two vertical edges, those at .1 and at C, and four horizontal edges, theupper ones AB and BC, and the lower ones AD and DC, are the edges which willcast shadows to give the shadow shape. Deal with them in the order suggestedby the numbers i to 6 in the figure
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisheretcetc, bookyear191
