Oblique

Oblique drawing is the crudest '3D' drawing method but the easiest to master. Oblique is not really a '3D' system but a 2 dimensional view of an object with 'forced depth'.

When using oblique the side of the object you are looking at is drawn in two dimensions, i.e. flat. The other sides are drawn in at 45 degrees but instead of drawing the sides full size they are only drawn with half the depth creating 'forced depth' adding an element of realism to the object.

Even with this 'forced depth', oblique drawings look very unconvincing to the eye. For this reason oblique is rarely used by professional designer and engineers.

How to draw an object using oblique

Oblique with 'foreshortening'

The side views are drawn in at a 45 degree angle. Standard practice is to 'foreshorten' the side views to provide a more convincing view of an object. To foreshorten the side views, the objects side measurements are halved. In this case, the sides are 50 mm long, but they have been drawn in at 25 mm.

Oblique with no 'foreshortening

This view is drawn at full size. Notice how circle looks elongated