gnuplot documentation

104 gnuplot 4.3 70 SET-SHOW
passes the grid lines through the hidden line removal machinery instead. These options actually affect
not only the grid, but also the lines output by set border and the various ticmarks (see set xtics
(p. 143)).
Z grid lines are drawn on the bottom of the plot. This looks better if a partial box is drawn around the
plot — see set border (p. 89).
70.25 Hidden3d
The set hidden3d command enables hidden line removal for surface plotting (see splot (p. 150)).
Some optional features of the underlying algorithm can also be controlled using this command.
Syntax:
set hidden3d {defaults} |
{ {{offset } | {nooffset}}
{trianglepattern }
{{undefined } | {noundefined}}
{{no}altdiagonal}
{{no}bentover} }
unset hidden3d
show hidden3d
In contrast to the usual display in gnuplot, hidden line removal actually treats the given function or
data grids as real surfaces that can’t be seen through, so parts behind the surface will be hidden by it.
For this to be possible, the surface needs to have ’grid structure’ (see splot datafile (p. 150) about
this), and it has to be drawn with lines or with linespoints.
When hidden3d is set, both the hidden portion of the surface and possibly its contours drawn on the
base (see set contour (p. 94)) as well as the grid will be hidden. Each surface has its hidden parts
removed with respect to itself and to other surfaces, if more than one surface is plotted. Contours drawn
on the surface (set contour surface) don’t work.
Labels and arrows are always visible and are unaffected. The key box is never hidden by the surface.
As of gnuplot version 4.2, set hidden3d also affects 3D plotting styles with points, with labels,
and with vectors, even if no surface is present in the graph. Individual plots within the graph may
be explicitly excluded from this processing by appending the extra option nohidden3d to the with
specifier.
Hidden3d does not affect solid surfaces drawn using the pm3d mode. To achieve a similar effect for
pm3d surfaces, use instead set pm3d depthorder.
Functions are evaluated at isoline intersections. The algorithm interpolates linearly between function
points or data points when determining the visible line segments. This means that the appearance of a
function may be different when plotted with hidden3d than when plotted with nohidden3d because
in the latter case functions are evaluated at each sample. Please see set samples (p. 129) and set
isosamples (p. 105) for discussion of the difference.
The algorithm used to remove the hidden parts of the surfaces has some additional features controllable
by this command. Specifying defaults will set them all to their default settings, as detailed below.
If defaults is not given, only explicitly specified options will be influenced: all others will keep their
previous values, so you can turn on/off hidden line removal via set {no}hidden3d, without modifying
the set of options you chose.
The first option, offset, influences the linestyle used for lines on the ’back’ side. Normally, they are
drawn in a linestyle one index number higher than the one used for the front, to make the two sides of
the surface distinguishable. You can specify a different line style offset to add instead of the default 1,
by offset . Option nooffset stands for offset 0, making the two sides of the surface use the
same linestyle.
Next comes the option trianglepattern . must be a number between 0
and 7, interpreted as a bit pattern. Each bit determines the visibility of one edge of the triangles each
surface is split up into. Bit 0 is for the ’horizontal’ edges of the grid, Bit 1 for the ’vertical’ ones, and