set pm3d depth lighting primary 0.7 specular 0.3 set object rect from sc 0,0 to sc 1,1 behind fc "#003344" 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 set out "shell000.png" 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] 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) splot x(u,v),y(u,v),z(u,v) w pm3d !display "shell000.png"