A single point:
  px,py

A pair of points
  px1,py1, px2,py2

An arc:
  cx, cy, cr, lang, rang
  ax, ay, ar, lang, rang

A line segment:
  x1,y1, x2,y2

A seglist:
  segl={2,3:4,5:6,7}

A ray:
  rx,ry,ra


utgen cases.utf id=N out.scn
  draw_arc_center=true
  draw_arc_edges=true
  draw_pt_labels=true
  draw_seg_labels=true