Trimetric Projections:

Trimetric projections are the third subclass of axonometric projections that allows the viewer freedom in choosing the components of a view plane normal (Hill, 1990). In this class, the view plane normal makes different angles along with each major axis as no two components of normal have the similar value. A trimetric view displays different orientations by placing different amounts of emphasis on the faces. Trimetric projections contain a potential disadvantage in that measurement of lines along the axes is hard because of a difference in scaling factors.

Illustrated how this unequal-foreshortening characteristic affects line measurements along different axes. A trimetric projection, along the correct orientation, may offer a realistic and natural view of an object (Hill, 1990).