# set terminal pngcairo  background "#ffffff" enhanced font "arial,8" fontscale 1.0 size 540, 384 
# set output 'hidden2.1.png'
set style fill   solid 0.50 border
unset key
set isosamples 25, 25
set hidden3d front offset 1 trianglepattern 3 undefined 1 altdiagonal bentover
set style data lines
set xyplane at 0
set title "Mixing pm3d surfaces with hidden-line plots" 
set xrange [ * : * ] noreverse writeback
set x2range [ * : * ] noreverse writeback
set yrange [ * : * ] noreverse writeback
set y2range [ * : * ] noreverse writeback
set zrange [ * : * ] noreverse writeback
set cbrange [ -1.00000 : 1.00000 ] noreverse nowriteback
set rrange [ * : * ] noreverse writeback
set palette rgbformulae 31, -11, 32
set colorbox vertical origin screen 0.9, 0.2 size screen 0.05, 0.6 front  noinvert bdefault
f(x,y) = sin(-sqrt((x+5)**2+(y-7)**2)*0.5)
NO_ANIMATION = 1
splot f(x,y) with pm3d, x*x-y*y with lines lc rgb "black"