Young, George, jr, Baxter, Hubert Eugene, joint author · New York, The Macmillan Co. · leaf 270
other cutting planes. The shade line ghl: is established by using the projection ona V plane parallel to a light ray as indicated at HA. Usingthis view, we draw the light ray hs tangent to the sphere,constructing the angle 6 as shown in Fig. 226. This line isthe top element of a cyHnder tangent to… … Fig. 236 254 DESCRIPTIVE GEOMETRY [XII, § 215 215. To Cast the Shadow of a Curved Line on a CurvedSurface. Let the curve be made the directrix of a cylinder,or of a cone in the case of a near-by source of light. Thiscylinder or cone defines the umbra and its intersection with thegiven surface…
Geometry, Descriptive
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