Two-dimensional arcs, approximated by cubic bezier curves.
Given a start angle
s and an end angle
path of a radius one arc counterclockwise between the two angles.
arc s e
bezierFromSweep s constructs a series of
Cubic segments that
start in the positive y direction and sweep counter clockwise
s radians. If
s is negative, it will start in the
negative y direction and sweep clockwise. When
s is less than
0.0001 the empty list results. If the sweep is greater than tau
then it is truncated to tau.