Sweeping a polyline produces a surface composed of many faces. The unbroken helix in the example Helix with cull set false then true is produced by this code (plus a surrounding put rotation to make an interesting view; this has been omitted).
def K [0,0,1] sweep[cull=false] { 60, rotate(10, (0,0,0), [K]) then translate(1/6 * [K]) } line[linewidth=2pt](-1,0)(1,0)Again, 60 segments of the helix are produced by connecting 61 instances of the swept line. Options applied to the sweep, here cull=false, are treated as options for the generated polygon or polyline. Options of the swept line itself, here linewidth=2pt, are ignored, though with a warning. This def is a vector definition, which must be referenced with square brackets, e.g. [foo].