# set terminal png transparent nocrop enhanced font arial 8 size 420,320 
# set output 'surface1.2.png'
set grid nopolar
set grid xtics nomxtics ytics nomytics noztics nomztics \
 nox2tics nomx2tics noy2tics nomy2tics nocbtics nomcbtics
set grid layerdefault
set samples 21, 21
set isosamples 11, 11
set title "3D gnuplot demo" 0.000000,0.000000  font ""
set xlabel "X axis" -3.000000,-2.000000  font ""
set xrange [ -10.0000 : 10.0000 ] noreverse nowriteback
set ylabel "Y axis" 3.000000,-2.000000  font ""
set yrange [ -10.0000 : 10.0000 ] noreverse nowriteback
set zlabel "Z axis" -5.000000,0.000000  font ""
splot x**2+y**2, x**2-y**2