# set terminal pngcairo  background "#ffffff" enhanced font "arial,10" fontscale 1.0 size 600, 400 
# set output 'surface1.1.png'
set grid nopolar
set grid xtics nomxtics ytics nomytics noztics nomztics \
 nox2tics nomx2tics noy2tics nomy2tics nocbtics nomcbtics
set grid layerdefault   linetype -1 linecolor rgb "gray"  linewidth 0.200,  linetype -1 linecolor rgb "gray"  linewidth 0.200
set hidden3d back offset 1 trianglepattern 3 undefined 1 altdiagonal bentover
set style data lines
set title "3D surface from a grid (matrix) of Z values" 
set xrange [ -0.500000 : 4.50000 ] noreverse nowriteback
set yrange [ -0.500000 : 4.50000 ] noreverse nowriteback
$grid = <5 line data block>
splot '$grid' matrix with lines notitle