Parallel curves of cubic Béziers

The problem of parallel or offset curves has remained challenging for a long time. Parallel curves have applications in 2D graphics (for drawing strokes and also adding weight to fonts), and also robotic path planning and manufacturing, among others. The exact offset curve of a cubic Bézier can be described (it is an analytic curve of degree 10) but it not tractable to work with. Thus, in practice the approach is almost always to compute an approximation to the true parallel curve. A single cubic Bézier might not be a good enough approximation to the parallel curve of the source cubic Bézier, so in those cases it is sudivided into multiple Bézier segments. A number of algorithms have been published, of varying quality.