This is a port of https://bl.ocks.org/mbostock/3916621 to D3 v4 and an attempt to be able to use much higher precision without affecting smoothness. The idea is to precalculate the resampled path before the transision starts, during its delay. The result is a big jump in all but the first transition because of problems (?) with D3 timer:
https://github.com/d3/d3-timer/issues/26
https://github.com/d3/d3-timer/issues/27
Actually, what I really want to do is not to use much higher precision, but to do this type of path tweening on many paths simultaneously. This was just an easier way to illustrate the idea and the problem.