x(u,v) = u*(1+0.5*cos(v))*cos(u)
y(u,v) = 0.5*u*sin(v)
z(u,v) = -u*(1+0.5*cos(v))*sin(u)
#
set pm3d depth lighting primary 0.7 specular 0.3
set palette rgb 8,7,27
set samples 128
set isosamples 48
unset border
unset tics
unset colorbox
unset key
set parametric
set xyplane 0
set view 70,25, 1.9, 1.3
set term pngcairo size 360,360 background "#003344"


c = 3*pi*1.4
d = 1.9
set urange [0:3*pi] 
set vrange [-pi:pi]
set xrange [-c-d:c-d]
set yrange [-c:c]
set zrange [-c-d:c-d]

N = 30
do for [i = 1:N+10] {
   j = i > N ? N : i
   set ur [3*pi*(N-j)/N:3*pi]
   set out sprintf("im%03d.png", i)
   splot x(u,v),y(u,v),z(u,v) w pm3d
}
system("convert -adjoin  -delay 10 im*.png shell0m.gif")
system("rm im*.png")