Depth can be expressed in figure drawing by applying the principles of linear perspective and foreshortening. Depth is also expressed with the light and shadows of the subject.
Linear perspective implies depth through the size and placement of elements. Closer elements appear larger to the viewer. Horizon and vanishing points are features of linear perspective, though they are not always obvious to the viewer.
The horizon line is where the land and sky meet, and vanishing points are where parallel elements converge in the distance on the horizon.
Though it is helpful to understand the principles of linear perspective, it is seldom necessary to plot out the horizon and vanishing points when drawing figures.
With this straight-on view, the observer is looking across at the scene. The horizon is at the eye level of the adult female figure with a single vanishing point behind the figure.
By moving the vanishing point to the far right, the figures are seen in three-quarter view. From this view, a second vanishing point is noticeable on the left, making this a two-point perspective drawing. Though viewed at an angle, the horizon still rests at the eye level of the adult figure. Notice that the figures of this scene display more depth than the previous example.
From this view you’re looking down on the scene at an angle. Notice that the vanishing points are along the horizon, the same as the previous drawing, but the horizon has moved above the figures. Looking down at this angle can make the subject feel distant or removed from the viewer.
Foreshortening implies depth by shortening the length of the individual features of a subject when viewed straight on. Foreshortening uses the principles of linear perspective on specific features of the subject.
In this drawing, the portion of the arm that is extended outward toward the viewer appears shortened and thus suggests depth through foreshortening.
Foreshortening will not look awkward if done correctly. In this drawing, the arms and legs of the figure are foreshortened in places, most evidently in the arm and leg just above the right knee. The other arm and leg are foreshortened also, although not as noticeable. Foreshortening doesn’t just apply to figures. In this drawing, the guitar is also foreshortened.