complex(x,y)=x*{1,0}+y*{0,1}
mandel(x,y,z,n) = \
 (abs(z) > 2.0 || n >= 250) ? log(n): mandel(x,y,z*z+complex(x,y),n+1)
a=-0.38
b=-0.612
#
set pm3d depth 
set palette rgb -6,-15,-7
unset colorbox 
set ticslevel 0
unset ztics
unset key
set samples 100
set isosamples 100
set size square

set term pngcairo fontscale 0.5 size 480,480
set out "julia.png"
set multiplot layout 2,2
splot [-0.5:0.5][-0.5:0.5] mandel(a,b,complex(x,y),0) w pm3d     
set pm3d map
splot [-0.5:0.5][-0.5:0.5] mandel(a,b,complex(x,y),0) w pm3d    
#
a=-0.50
b=0.612
#
set view 60,30
set pm3d at s
splot [-0.5:0.5][-0.5:0.5] mandel(a,b,complex(x,y),0) w pm3d     
set pm3d map
splot [-0.5:0.5][-0.5:0.5] mandel(a,b,complex(x,y),0) w pm3d    

set nomultiplot