With a 3dpoly one can have different elevations at each point.
I have quite a few drawings in 2d that I need to convert over to 3d for a cnc system.
I wrote a lisp routine to read the 3dpoly points and store the x,y,z, coordinates at each point into a file.
I want to get a ways from running this on a 2d polyline and hand editing the text file, putting the z values in. If I can automate the process I could elimates some errors.