Rewrote with CoffeeScript and refactored with OO design

I used your code as an excuse to improve my knowledge of CoffeeScript.
Now the spiral is an object that computes only its segments (with its own shadow). I added the object tree that is a combination of spirals.
Finally Screen takes care of creating the objects to draw and, using the Projection class generates a conversion between the 3D model of the object and the 2D screen.

I hope you can appreciate this