It is possible, when making 3D plots from data files, for the data to be interpreted in spherical or cylindrical coordinates rather than the default Cartesian system. For details, type help set mapping
. We will give an example of using the cylindrical mapping to conveniently draw a shape with cylindrical symmetry.
The previous figure is a perspective view of a surface that somewhat resembles a Christmas tree ornament. The relevant feature of this surface is that it has rotational symmetry around the z (vertical) axis, which means that it is most naturally expressed in cylindrical coordinates.
set mapping cylindrical
unset tics
unset border
set hidden
set xrange [-pi : pi]
set yrange [-pi : pi]
set zrange [0 : pi]
set iso 60
unset key
splot '++' using 1:2:(sin($2)) with lines