There are no zebras here. Just stripes on a flat surface. However, the stripes give the illusion of a fully formed animal. An artist will think of these stripes as “contour lines.” That is, lines whose shape and placement make them appear to lie along the surface of a real zebra’s three-dimensional body. These contour lines reveal powerful haunches, pear-shaped bellies, bulging neck and chest muscles, and the intricate connection of leg bones with tendons.
Artists use contour lines to create an illusion of volume. In 1717 Jean-Antoine Watteau, painter of French aristocrats, used stripes to follow the ins and outs of rumpled cloth. The “line” can be a stripe, a hemline, a seam, a fold in cloth, the edge of a shadow – whatever lies along a surface and reveals volume. Watteau added to his stripes’ shaping effect by darkening them in the shaded areas and letting them disappear where the light hit the cloth directly. He also uses the edges of shadows as contour lines, including where they run counter to the stripes. For example, on the model’s right sleeve and twice in the train of her dress, you can see the shadow’s-edge contour line where the lighted edge of a deep fold casts a shadow on the opposite side. You can also see where a shadow’s edge clarifies the flatness of the floor.
Contour lines are not only important to great, complex paintings of the past, they are key components of the quick, abbreviated drawings, loose sketches, and cartoons of recent decades. For example, the 1960s Magazine Illustrator David Levine used contour lines to say a lot with a little in this caricature of John L. Sullivan, 1889 World Heavyweight Bare-knuckle Boxing Champion: he used Sullivan’s belt as a contour line to describe the equator of his belly. Levine also suggests a vertical contour running from the hair on Sullivan’s chest down to the crease of his belly-button. With very few marks, the two suggested lines, like latitude and longitude, define a globe-like volume.
Artists watch for potential contour lines. I saw the potential contour line of a bird’s foot curled around a branch. So I took its picture. As I copied the picture I stressed the potential contour lines of the bird’s feathers lying along its body, following its form lengthwise. I also took advantage of the ends of the feathers that suggested lines rounding the body crosswise. Then, where I thought the branch still looked a little flat, I invented a shadow that fell on it so the shadow’s edge would become a contour line that made the branch look round.