set pm3d depth lighting primary 0.75 set object rect from sc 0,0 to sc 1,1 behind fc "#003344" set palette rgb 8,7,27 set samples 256 set isosamples 32 unset border unset tics unset colorbox unset key set xyplane 0 set view 65,30, 0.6,3 set term pngcairo size 360,360 set out "shell003.png" set parametric set urange[-18*pi:0] set vrange[-7*pi/4:pi/4] cot(x)=1/tan(x) x(u,v)=(A*sin(b)*cos(u)+R*cos(v)*cos(u)-R*sin(m)*sin(v)*sin(u))*exp(u*cot(a)) y(u,v)=(-A*sin(b)*sin(u)-R*cos(v)*sin(u)-R*sin(m)*sin(v)*cos(u))*exp(u*cot(a)) z(u,v)=(-A*cos(b) + R*sin(v)*cos(m))*exp(u*cot(a)) D=1;a=pi/180*88.1;b=pi/45;m=pi/180;A=22.2;R=2.3 set zrange [:] splot x(u,v), y(u,v), z(u,v) w pm3d !display shell003.png