The distinguishing feature of axonometric projection, as
compared to multi view projection, is the inclined position of
the object with respect to the plane of projection. Since the
principal edges and surfaces of the object are inclined to the
plane of projection, the lengths of the lines, the sizes of the
angle, and the general proportions of the object vary with the
infinite number of possible positions in which the object may
be placed with respect to the plane of projection. Three of
these are shown below.
In these cases the edges of the cube are inclined to the plane
of projection, and therefore foreshortened. The degree of
foreshortening of any line depends on its angle with the plane
of projection; the greater the angle the greater the
foreshortening. If the degree of the foreshortening is
determined for each of the three edges of the cube which
meet at one corner, scales can be easily constructed for
measuring along these edges or any other edges parallel to
them. It is customary to consider the three edges of the cube
which meet at the corner nearest to the observer as the
axonometric axes.
Axonometric projections are classified as
a) Isometric projection
b) Dimetric Projection
c) Trimetric Projection, depending up on the number of
scales of reduction required.