The relationship between forms and the space surrounding them is known as the figure/ground relationship. Looking at the image of the circle to the left, notice that the outline of the circle defines two areas of space: the circle's interior space, also called the figure, and the space surrounding it, known as the ground. You might think of the ground as the setting, and the figure as the object that serves as the focus for the piece — for instance, a tree on a distant hill, or a flower in close-up.

Made in the shade
When shading is added to the circle, the distinctions between the figure and the ground become clearer. In the top image, the shaded figure appears to project forward from the empty ground. In the bottom image, the empty figure appears to recede backward from the shaded ground. Using the simple device of shading, we can increase the illusion of space by suggesting volume and depth.