Combining surfaces with images

It is possible to plot a surface and its projection as a color image on the x-y plane on the same graph. The two simultaneous views of the same data or function can be useful to bring out the topography of a complex surface.

The previous figure shows a simple trigonometric function of two variables displayed as a surface with its values simultaneously encoded into colors (or gray values) at the base of the plot.

How to do it…

The following script produces the previous figure as its output:

set iso 40
set samp 40
unset key
set xrange [-pi:pi]
set yrange [-pi:pi]
f(x,y) = sin(x)*cos(y)
set hidden front
set xyplane at -1
splot f(x,y) with pm3d at b, f(x,y) with lines

How it works…

The new features we are combining to produce this graph are in the highlighted lines in the code sample. Let's look at the last command first. The first part of the splot command plots the function f(), which is defined three lines above, as a colored surface at the base of the plot; this...