There are various ways of depicting aerial perspective.

  1. Change the colour. (Background scenery such as distant mountains tend to look more blue.)
  2. Change the opacity. (The further away, the less vivid the colours.)
  3. Make use of blur. (Background scenery might be more blurry if you want to draw attention to your foreground image.)
  4. Darken foreground lines.
  5. Change the amount of detail.

 

thick lines

Here’s a rather extreme example of line thickening in the foreground.

 

Or, you can stylize your illustrations, making up your own technique.

  1. Use white lines as background scenery.
  2. Use unfilled objects (with dark lines) as background scenery.
Heidi

white lines forming a gesture of mountains in the background

The Snow Queen

thin white lines for the background building, thicker lines for the trees in the middle ground, full colour for the children in the foreground

Rootabaga Stories

In Drahos Zac’s illustrations for The Pied Piper, there may be ominous reasons for avoiding the sepia fill on background buildings: The inhabitants of those particular buildings may have already died. This theory holds up when you consider some of the foreground characters are also left unfilled. This feels reminiscent of ghosts.

Pied Piper Drahos Zak drahos zak2

Here, Maurice Sendak does something a bit different.

The Wheel On The School