# set terminal pngcairo  transparent enhanced font "arial,10" fontscale 1.0 size 500, 350 
# set output 'contours.6.png'
set view 60, 30, 0.85, 1.1
set samples 20, 20
set isosamples 21, 21
set contour surface
set cntrparam levels auto 10
set title "3D gnuplot demo - contour plot on surface" 
set xlabel "X axis" 
set ylabel "Y axis" 
set zlabel "Z axis" 
set zlabel  offset character 1, 0, 0 font "" textcolor lt -1 norotate
splot x**2-y**2