#
# PM3D surfaces are not included in the calculation of hidden line removal.
# However, you can approximate this by drawing the surface twice,
# once "with pm3d" to produce the surface you want to show, and once 
# "with lines lt -2" to include the same surface in hidden3d calculations.
# The "lt -2" makes the hidden3d copy of the surface invisible.
#
set hidden3d front
set isosamples 25,25
set xyplane at 0
unset key

set palette rgbformulae 31,-11,32
set style fill solid 0.5
set cbrange [-1:1]

set title "Mixing pm3d surfaces with hidden-line plots"

f(x,y) = sin(-sqrt((x+5)**2+(y-7)**2)*0.5)
splot f(x,y) with pm3d, x*x-y*y with lines lt 1 lc rgb "#000000", \
      f(x,y) with lines lt -2 notitle


Click here for minimal script to generate this plot

#
# Another example of pm3d hidden surface removal,
# this time using pm3d depth-ordering
#
set multiplot title "Interlocking Tori"
set title "PM3D surface\nno depth sorting"

set parametric
set urange [-pi:pi]
set vrange [-pi:pi]
set isosamples 50,20

set origin -0.02,0.0
set size 0.55, 0.9

unset key
unset xtics
unset ytics
unset ztics
set border 0
set view 60, 30, 1.5, 0.9
unset colorbox

set pm3d scansbackward
splot cos(u)+.5*cos(u)*cos(v),sin(u)+.5*sin(u)*cos(v),.5*sin(v) with pm3d, \
      1+cos(u)+.5*cos(u)*cos(v),.5*sin(v),sin(u)+.5*sin(u)*cos(v) with pm3d

set title "PM3D surface\ndepth sorting"

set origin 0.40,0.0
set size 0.55, 0.9
set colorbox vertical user origin 0.9, 0.15 size 0.02, 0.50
set format cb "%.1f"

set pm3d depthorder
splot cos(u)+.5*cos(u)*cos(v),sin(u)+.5*sin(u)*cos(v),.5*sin(v) with pm3d, \
      1+cos(u)+.5*cos(u)*cos(v),.5*sin(v),sin(u)+.5*sin(u)*cos(v) with pm3d

unset multiplot


Click here for minimal script to generate this plot