Orthographic Projections, Continued
Multiview
projections
Multiview projections are the second major subdivision of orthographic
projections.
Principal views
There are six principal views in a multiview orthographic projection. These
are the front, back, top, bottom, and left- and right-side views. Of these
views or planes, three are referred to as primary planes of projection
(vertical, horizontal, and profile). Most objects are adequately represented
by the three primary planes.
Angles of
projection
The primary planes intersect each other at right angles. The angles between
the horizontal and vertical planes are described as first, second, third, and
fourth angles of projection. In theory, you can place an object in any of
these angles of projection and draw or project its image onto the projection
planes, which in turn could be rotated onto the plane of your drawing paper.
Only first- and third-angle projection have a practical application today.
Figure 6-23 shows the angles of projection in a multiview projection.
Figure 6-23.—Angles of projection in multiview projections.
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