set pm3d interpolate 0,0 depth lighting primary 0.8 specular 0.5
set object rect from sc 0,0 to sc 1,1 behind fc "#114400"
set palette defined (0 "#3333ee", 1 "#3333ee")
set samples 128
set isosamples 64
unset border
unset tics
unset colorbox
unset key
set xyplane 0
set view 75,30, 1.8,
set term pngcairo size 360,360
set out "bottle001.png"
set parametric

D = 0.7
# print D*exp(-3*(6-7))/(1+exp(-3*(6-7))) + (1.05-D)
R(u,v) = u > 6 ? D*exp(-3*(u-7))/(1+exp(-3*(u-7))) + (1.05-D) \
         : 0.9168 + 0.1*cos(2*pi*u/6)
x(u,v) = R(u,v)*cos(v)
y(u,v) = R(u,v)*sin(v)
z(u,v) = u
set urange [0:10] 
set vrange [-pi:pi]
set zrange [0:10]
set xrange [-5:5]
set yrange [-5:5]

splot x(u,v), y(u,v), z(u,v) w pm3d
!display bottle001.png