Mô-đun extrude xoắn ốc cho OpenSCAD

There is no built-in module for helical extrude. The twist function of linear_extrude starts to break at higher twist rates, like with threads. Uses polyhedron().

usage is:

helix_extrude(
   points, //2D pt array, the kind you would use with polygon(). Pts order should be CCW.
   pitch, //Distance from one point of the profile to the corresponding pt on the next.+RH, -LH.
   loops ,//How many times you want to want to wrap
   fn); //Number of facets per single turn, same as $fn

Loops cannot overlap, it will not render.

There might be some chaff in the script, won't affect much. It's just my programming style. I brainstorm, and blast as many variables and code as I can. Then I start putting things together.