using Gnuplot
empty!(Gnuplot.options.init)
push!( Gnuplot.options.init, linetypes(:Set1_5, lw=1.5, ps=1.5))
function saveas(file; sx=550, sy=350, fs=0.8, term="svg")
    Gnuplot.save(term="$(term) size $(sx),$(sy) fontscale $(fs)", "$(file).svg")
end;

tube plot

U  = LinRange(0,10π, 80)
V = LinRange(0,2π, 20)
x = [(1-0.1*cos(v))*cos(u) for u in U, v in V]
y = [(1-0.1*cos(v))*sin(u) for u in U, v in V]
z = [0.1*(sin(v) + u/1.7 - 10) for u in U, v in V]
@gsp "set pm3d depthorder" :-
@gsp :- "set style fill transparent solid 0.7" "set view equal xyz"
@gsp :- x y z "w pm3d notit" "set xyplane -0.05" palette(:ice)
saveas("surface004");