class Magick::RVG::PathData

def smooth_curveto(abs, x2, y2, x, y, *coords)

the coordinates are relative.
true the coordinates are absolute, otherwise
If abs is
Add a smooth curveto (cubic Bezier) command.
def smooth_curveto(abs, x2, y2, x, y, *coords)
  @path << sprintf('%s%g,%g %g,%g ', (abs ? 'S' : 's'), x2, y2, x, y)
  # "multiple sets of coordinates may be specified to draw a polybezier"
  add_points(4, *coords)
end