Spirals

One of the classic shapes to construct in turtle logo is the Spiral.

The first way you write this program, is as a variation on a polygon. You go forward, you turn a bit, you go forward, you turn a bit. But you make it recursive, so that the amount you go forward can become smaller and smaller each time. Technically, this is called a 'spirangle'

If you look at that last example, we turned it around completely.

Instead of making a smaller and smaller line each time, we made a bigger and bigger line. (A ratio of 1.005) This created a spiral in the opposite direction! (Opposing chirality)

There is also an 'arc' function in Turtle graphics, that lets you draw smoother curves.

Swirls and spirals appear in nature in all kinds of places. In the seeds of a sunflower, in the vortex of a hurricane, in the horns of a goat, in the shell of a snail, in the curling fronds of a fern, in this guy's beard.

A man with a beard cut into a spiral shape.

External Links

 

Logo + Turtle graphics via Papert.