Spirograph (Epitrochoid)

The radius of the outer circle and the center offset will determine the curve that you will get. The center offset is how far the point generating the curve is from the center of the outer circle. In a real Spirograph, the offset cannot be greater than the radius of the circle. However, try adjusting the center offset to be greater than the radius to get some interesting curves. When the radius of the outer circle equals the radius of the inner circle (that is, 2), the epitrochoid is known as a limacon. Adjust the size of the point to get a thinner or thicker curve. You can also adjust the speed of the animation with the speed slider. When you've changed a parameter, hit the clear trace button to erase the old curve. Use the pen circle button to show or to hide the generating circle and pen arrow.