I'm attempting to combine a surface plot with contours. Unfortunately, contours don't seem to play well. For instance, the lines all come out dashed and overlap the surface in a decidedly un-3D way.
I figured the best solution was to save contour data to a file and read it in. But I have no idea how to set gnuplot to plot this data at the base. If you have any suggestions, I'd appreciate them.
set border 15
set cntrparam levels incremental -2, 1
set samples 200
set isosamples 200,200
range = 0.75*pi
set xrange [-range:range]
set yrange [-range:range]
a = 1
f(x,y) = 2*cos(sqrt(3)*y*a)+4*cos(sqrt(3)/2.0*y*a)*cos(3*x*a/2)
set table 'tmp.dat'
set contour base
set view map
splot '++' u 1:2:(f($1,$2)) notitle
splot 'tmp.dat' u 1:2:(-6):(column(-2)) w l lw 2 lt -1 lc var notitle, \ '++' u 1:2:(f($1,$2)) w pm3d notitle