Descriptive geometry . r adopted, whenapplied to an actual object, always gives a view of its rightside; whereas a view of the left side may be decidedly prefer- a+ -> ef+- + a° Fig. 84. able. For this purjiose, P is viewed from its left side, that is,from left to right, and then projected so as to bring this sideinto the drawing surface. This method is shown for a point inthe first quadrant in Fig. 84. That this method is directlyopposite to that previously used is shown also by the line ab,Fig. 85. Since the H- and F-prejections of a and b show that z 1 / 3 4 t 1 / iIi bh- — i / i i bv- b
Descriptive geometry . r adopted, whenapplied to an actual object, always gives a view of its rightside; whereas a view of the left side may be decidedly prefer- a+ -> ef+- + a° Fig. 84. able. For this purjiose, P is viewed from its left side, that is,from left to right, and then projected so as to bring this sideinto the drawing surface. This method is shown for a point inthe first quadrant in Fig. 84. That this method is directlyopposite to that previously used is shown also by the line ab,Fig. 85. Since the H- and F-prejections of a and b show that z 1 / 3 4 t 1 / iIi bh- — i / i i bv- b / Fig. 85. these points are in the first and fourth quadrants respectively, the quadrants must appear in the profile projection as marked. In Fig. 86 the profile trace of the same plane Q is obtained, first, by looking from right to left, and then by looking from VI, § 64] THE PROFILE PLANE 45 left to right. Note that, since HQ is at 45° with the gi-oundline, PQ coincides with VQ in the tirst figure, and that the. Fig. 8(>. second figure is much the clearer, especially if some furtherconstruction is to be made with the plane Q. Hereafter we shall view P from either side; although, otherthings being equal, the direction from right to left will be pre-ferred. If the quadrants are numbered in every profile projec-tion, there should be no confusion, whichever view is used. 63. Conventional Placing of Left-side Views. When the pro-file projection of a solid object is made so as to show its leftside, it is customary to place this projection at the right of thefront elevation when the object is located in the first quadrant,and at the left of the front elevation when the object is locatedin the third quadrant. This is the reverse of the method ofplacing the view of the right side, as shown in Figs. 68 and 70.(See § 54.) Actual objects are rarely placed in the second orfourth quadrants, so that there is no fixed custom for locatingsuch views. 64. Second Method of Obtaining Pr
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