(5) A 3-D illuminated surface (in bw)
Instead of a mesh plot we may choose to show 3-D surfaces using
artificial illumination. For this example we will use
grdmath to make a grid file that
contains the surface given by the function
#!/usr/bin/env bash
# GMT EXAMPLE 05
#
# Purpose: Generate grid and show monochrome 3-D perspective
# GMT modules: grdmath, grdview, text, makecpt
# Unix progs: rm
#
gmt begin ex05
gmt grdmath -R-15/15/-15/15 -I0.3 X Y HYPOT DUP 2 MUL PI MUL 8 DIV COS EXCH NEG 10 DIV EXP MUL = sombrero.nc
gmt makecpt -C128 -T-5/5 -N
gmt grdview sombrero.nc -JX12c -JZ4c -B -Bz0.5 -BSEwnZ+t"z(r) = cos (2@~p@~r/8) @~\327@~e@+-r/10@+" -N-1+gwhite -Qs \
-I+a225+nt0.75 -C -R-15/15/-15/15/-1/1 -p120/30 --FONT_TITLE=50p,ZapfChancery-MediumItalic --MAP_TITLE_OFFSET=-1c
rm -f sombrero.nc
gmt end show
The variations in intensity could be made more dramatic by using grdmath to scale the intensity file before running grdview. For very rough data sets one may improve the smoothness of the intensities by computing them first with grdgradient and then pass them to grdhisteq. The shell-script above will result in a plot like the one in Figure.
![../_images/ex05.png](../_images/ex05.png)
3-D illuminated surface.