Before the advent of computers, various types of drawing machines were devised to create images.
Simple machines use a pen swinging freely on a pendulum to create images. More complex machines allowed the paper and the pen to swing independently, creating more complex images. Variants use a swinging container that pours paint onto a canvas as it swings, or even swinging lights that expose photographic film to create the image.
Other machines use cogs to control the motion of the pen. The Spirograph toy is the best known example.
With computer graphics we can create far more complex and precise images. Some techniques are described in this chapter.