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.

OBLIQUE PROJECTION

209

Under these conditions the oblique projection of a solid, one of
whose faces is in the plane of projection, will have the appearance
of a perspective drawing, and the system of projection is called
pseudo-perspective.
453. Problem 313. To make a pseudo-perspective of a cube.
In Fig. 191 let a'-b'-d'-e' represent the face of a cube in V.
Draw the lines d'-k', b'-g', and a'-f as in cabinet projection.
Make d'-c', b'-g', and a'-f' each equal to some fractional part, say
one third, of the edge of the cube. Connect k' and g', also g' and
ft, by straight lines, and a'-f'-g'-k'-d'-et
will be the pseudo-perspective of the cube.
FIG. 192 FIG. 193
Fig. 192 represents the pseudo-perspective of an irregular solid
some of whose edges are perpendicular to V and others parallel to V.
Lines which are in V or are parallel to V are represented in full
length, while lines which are perpendicular to V are represented
about one quarter of their original length.
Fig. 193 represents the pseudo-perspective of a connecting-rod
end, introducing the projections of curved lines.
Since in a pseudo-perspective drawing the length of lines in the
drawing have a known ratio to the lines which they represent,
the system may sometimes be advantageously employed in making
working drawings.