Hypotrochoid Drawer pull knobs (Customizable!)

Hypotrochoids are vecor shapes, created by revolving a circle of size r within a stationary circle of size R and tracing a point at distance d from the center of the smaller circle.  Probably the best known implementation of this is the toy known as a Spirograph. 

These knobs bring those beautiful roulette patterns to your furniture, with a customizer that lets you get as fancy or detailed with them as you want.

I borrowed some functions from JustinSDK's dotSCAD library (https://github.com/JustinSDK/dotSCAD) to simplify the line functions, specifically the polyline3d function.  rather than require end users to have the whole dotSCAD library I brought the relevant functions into my own project, commented at the bottom with details.

Be careful when rendering this and don't decrease the step2 value by too much. This is the frequency of the polygons on the outer perimeter of the knob.

The Rotations argument may be necessary to increase to have the pattern join back up (particularly with r greater than ½ of R)

Warning-Previews generate pretty quickly, so you can play with your settings and get a nice design. However rendering for export can be VERY slow thanks to the the hull function, which is used to smooth the outer edge. please be patient with it, especially when that last 5% seems to take forever.  If it just won't go on your computer, the hull() function on line 44 in the ring2() module can be commented out - you'll end up with a more faceted peremeter.

upate- Added an additional sample and tweaked the code to allow for the line weight on the design to be changable.  Also increased default values for Step and Step2 to reduce render time.