Orthographic Projections, ContinuedNormal andoblique lines(Continued)Figure 6-32 shows a pictorial drawing of a triangular object in the upper-leftcorner. The right side is presumed parallel to the profile plane of projection,the bottom view parallel to the horizontal plane, and the front view parallel tothe vertical plane. The line AB is oblique to all three planes. The truelength of AB is shown in the small triangle to the left of the single-viewprojection. It is the length of the hypotenuse of a triangle with the altitudeequal to the length of AB as it appears in the top view of the multiviewprojection. AB is foreshortened in all of the orthographic views.Figure 6-32.—Oblique lines foreshortened in all orthographicviews.Circles, arcs,and ellipsesIn multiview projections, a circle on surfaces parallel to the plane ofprojection appears as a circle. A circle on a surface that is oblique to theplane of projection appears as an ellipse.6-38

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