The orthogonal projection of an object can be obtained by imagining placing a plane next to the object to be represented and hitting it with a beam of rays parallel to each other and orthogonal to the projection plane.

A single projection is generally insufficient to provide a complete description of an object, so multiple independent projections of the same object are generally adopted.

To optimize the description, coordinated planes perpendicular to each other are used, in which we can identify the plan (view from above), the front (frontal view) and the side of the object (lateral view). These three projections, with the help of hidden lines, are generally sufficient to complete the description of the object.

This drawing technique guarantees a complete geometric description of the object, but very often is not easy to understand for the technically unprepared user.

For this reason, very often, for technical illustration for dissemination (think of car, motorcycle or boat magazines as an example) it is preferred to use other projection techniques such as axonometric or perspective projection.