Median line
Select several polylines and launch the command.
This function creates a "median" polyline, that is to say:
for each input vertex, other polylines are cut into segments which have the same length ratio,
then the gravity center is computed for each set of vertices,
finally, gravity centers are joined so as to create the median polyline.
Perspective view: green polylines: inputs, purple points: new vertices, red polyline: median polyline
