gnuplot>f(x,y)=cos(x)*(cos(x)+cos(y*sqrt(3)))
gnuplot>set contour
gnuplot>show view
view is 60 rot_x, 30 rot_z, 1 scale, 1 scale_z
gnuplot> set view 0,90,,
gnuplot> show view
view is 0 rot_x, 90 rot_z, 1 scale, 1 scale_z
gnuplot> replot
gnuplot> splot f(x,y) w l 15
gnuplot> set xrange[-3.15:3.15]
gnuplot> set yrange[-3.15:3.15]
gnuplot> replot