Visualisation of path features interpolates arcs with straight segments. The algorithm works fine except for some edge cases with a very soft curvature. This change introduces a minimum amount of 20 segments for each arc and/or helix, regardless of the arc radius and opening.
change: https://github.com/FreeCAD/FreeCAD/pull/410
issue: http://www.freecadweb.org/tracker/view.php?id=2825