# set terminal pngcairo  background "#ffffff" enhanced font "arial,10" fontscale 1.0 size 600, 400 
# set output 'rgb_variable.8.png'
unset key
set view 63, 58, 1, 1.4
set isosamples 40, 40
set xyplane at 0
set noxtics
set noytics
set ztics  norangelimit
set ztics   ("0" 0.00000)
set title "HSV coloring of pm3d surface\n(V=1)" 
set xlabel "H" 
set xrange [ 0.0100000 : 1.00000 ] noreverse nowriteback
set ylabel "S" 
set yrange [ 0.0100000 : 1.00000 ] noreverse nowriteback
set zrange [ 0.00000 : 1.00000 ] noreverse nowriteback
unset colorbox
rgb(r,g,b) = int(r)*65536 + int(g)*256 + int(b)
xrgb(r,g,b) = (g-b)/255. * cos(30.)
yrgb(r,g,b) = r/255. - (g+b)/255. * sin(30.)
RGB(R,G,B) =  int(255.*R) * 2**16 + int(255.*G) * 2**8  + int(255.*B)
f(x,y) = 0.4 + sin(sqrt(100.*x**2+100.*y**2))        / (1.5*sqrt(100.*x**2+100.*y**2))
GPFUN_rgb = "rgb(r,g,b) = int(r)*65536 + int(g)*256 + int(b)"
GPFUN_xrgb = "xrgb(r,g,b) = (g-b)/255. * cos(30.)"
GPFUN_yrgb = "yrgb(r,g,b) = r/255. - (g+b)/255. * sin(30.)"
GPFUN_RGB = "RGB(R,G,B) =  int(255.*R) * 2**16 + int(255.*G) * 2**8  + int(255.*B)"
GPFUN_f = "f(x,y) = 0.4 + sin(sqrt(100.*x**2+100.*y**2))        / (1.5*sqrt(100.*x**2+100.*y**2))"
splot '++' using 1:2:(f($1,$2)):(hsv2rgb($1,$2,1.0))        with pm3d lc rgb variable