timings, and better handling of obtuse angles

smarter vector interpolation

check for intersections closer to the ends of the segments

only cull interior overlaps for the middle of thread segments

don't blow up if the threads overlap due to excessive width

convert thread segments into polygons

z-interpolation was not actually needed here

add knot interpolation routines ("knot shape")

faster knot generation

knot generation has been moved to the Builder class

update README

nix the svg output, since it wasn't working right

get over/under calculations working right

compute midpoint of ignored edges better

follow individual threads