# set terminal pngcairo  transparent enhanced font "arial,10" fontscale 1.0 size 600, 400 
# set output 'surface1.2.png'
set grid nopolar
set grid xtics nomxtics ytics nomytics noztics nomztics nortics nomrtics \
 nox2tics nomx2tics noy2tics nomy2tics nocbtics nomcbtics
set grid layerdefault   lt 0 linecolor 0 linewidth 0.500,  lt 0 linecolor 0 linewidth 0.500
set label 1 "This is the surface boundary" at -10.0000, -5.00000, 150.000 center norotate back nopoint
set arrow 1 from -10.0000, -5.00000, 120.000 to -10.0000, 0.00000, 0.00000 nohead back nofilled linewidth 1.000 dashtype solid
set arrow 2 from -10.0000, -5.00000, 120.000 to 10.0000, 0.00000, 0.00000 nohead back nofilled linewidth 1.000 dashtype solid
set arrow 3 from -10.0000, -5.00000, 120.000 to 0.00000, 10.0000, 0.00000 nohead back nofilled linewidth 1.000 dashtype solid
set arrow 4 from -10.0000, -5.00000, 120.000 to 0.00000, -10.0000, 0.00000 nohead back nofilled linewidth 1.000 dashtype solid
set style increment default
set samples 21, 21
set isosamples 11, 11
set style data lines
set title "3D surface from a function" 
set xlabel "X axis" 
set xlabel  offset character -3, -2, 0 font "" textcolor lt -1 norotate
set xrange [ -10.0000 : 10.0000 ] noreverse nowriteback
set x2range [ * : * ] noreverse writeback
set ylabel "Y axis" 
set ylabel  offset character 3, -2, 0 font "" textcolor lt -1 rotate
set yrange [ -10.0000 : 10.0000 ] noreverse nowriteback
set y2range [ * : * ] noreverse writeback
set zlabel "Z axis" 
set zlabel  offset character -5, 0, 0 font "" textcolor lt -1 norotate
set zrange [ * : * ] noreverse writeback
set cbrange [ * : * ] noreverse writeback
set rrange [ * : * ] noreverse writeback
## Last datafile plotted: "$grid"
splot x*y