Elements of descriptive geometry, with applications to isometric projection and othe forms of one-plane projection; a text-book for colleges and ingineering schools by O. E. Randall.

ISOMETRIC PROJECTION

199

Make o'-a' and o'-d' each equal to the edge of the cube.
Through a' draw a'-e' parallel to o'-d. Through d' draw d'-e'
parallel to o'-a' and intersecting a'-e' at e'. The figure o'-a'-e'-d'
represents the isometric projection of the upper face of the cube.
Make o'-b' equal to the edge of the cube. Through a' draw
a'-f parallel to o-b'. Through e
b' draw b'-f' parallel to o'-a and z
intersecting a'-f' at f'. The fig- \
ure o'-a'-f'-b' represents the isometric projection of the right-hand -- -- -
face of the cube.
'Through b6 draw b'-g' parallel
to o'-d'. Through d' draw d'-g'
parallel to o'-b' and intersecting
b'-g' at g'. The figure o'-b'-g'-d'
represents the isometric projection
of the left-hand face of the cube.
The figure e'-a'-f'-b'-g-d' is the isometric projection of the
cube.
To determine the shade lines of the cube.
With the source of light in its new position, as stated above,
p, the three faces 0-E, 0- G, and
G-E will be in the light, and the
7r1<, m vm1 three remaining faces will be in
zi' T x' the dark. Therefore the visible
kf/' T a shade lines are G-B, B-O, O-A,
and A-E.
439. Problem 304. To make an
isometric projection of a square
da^ ~ pedestal supporting a square prismatic pillar.
See Fig. 174. Place the upper
FIG. 174 front vertex of the pedestal at the
origin 0. Make o'-a' and of-bf each equal to the side of the square
pedestal; also make o'-d' equal to the altitude of the pedestal.
The pedestal is now completed by drawing through a', b', and d'
straight lines parallel to the proper axes.