gnuplot documentation
gnuplot documentation
gnuplot documentation
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120 <strong>gnuplot</strong> 4.3 70 SET-SHOW<br />
unset pm3d<br />
Color surface is drawn if data or function style is set to pm3d globally or via ’with’ option, or if the<br />
option implicit is on — then the pm3d surface is combined with the line surface mesh. See bottom of<br />
this section for mode details.<br />
Color surface can be drawn at the base or top (then it is a gray/color planar map) or at z-coordinates of<br />
surface points (gray/color surface). This is defined by the at option with a string of up to 6 combinations<br />
of b, t and s. For instance, at b plots at bottom only, at st plots firstly surface and then top map,<br />
while at bstbst will never by seriously used.<br />
Colored quadrangles are plotted one after another. When plotting surfaces (at s), the later quadrangles<br />
overlap (overdraw) the previous ones. (Gnuplot is not virtual reality tool to calculate intersections of<br />
filled polygon meshes.) You may try to switch between scansforward and scansbackward to force<br />
the first scan of the data to be plotted first or last. The default is scansautomatic where <strong>gnuplot</strong><br />
makes a guess about scans order. On the other hand, the depthorder option completely reorders the<br />
qudrangles. The rendering is performed after a depth sorting, which allows to visualize even complicated<br />
surfaces; see help pm3d depthorder (p. ??) for more details.<br />
If two subsequent scans do not have same number of points, then it has to be decided whether to<br />
start taking points for quadrangles from the beginning of both scans (flush begin), from their ends<br />
(flush end) or to center them (flush center). Note, that flush (center|end) are incompatible with<br />
scansautomatic: if you specify flush center or flush end and scansautomatic is set, it is silently<br />
switched to scansforward.<br />
If two subsequent scans do not have the same number of points, the option ftriangles specifies whether<br />
color triangles are drawn at the scan tail(s) where there are not enough points in either of the scan. This<br />
can be used to draw a smooth map boundary.<br />
Clipping with respect to x, y coordinates of quadrangles can be done in two ways. clip1in: all 4 points<br />
of each quadrangle must be defined and at least 1 point of the quadrangle must lie in the x and y ranges.<br />
clip4in: all 4 points of each quadrangle must lie in the x and y ranges.<br />
There is a single gray/color value associated to each drawn pm3d quadrangle (no smooth color change<br />
among vertices). The value is calculated from z-coordinates from the surrounding corners according to<br />
corners2color . The options ’mean’ (default), ’geomean’ and ’median’ produce various kinds<br />
of surface color smoothing, while options ’min’ and ’max’ choose minimal or maximal value, respectively.<br />
This may not be desired for pixel images or for maps with sharp and intense peaks, in which case the<br />
options ’c1’, ’c2’, ’c3’ or ’c4’ can be used instead to assign the quadrangle color based on the z-coordinate<br />
of only one corner. Some experimentation may be needed to determine which corner corresponds to ’c1’,<br />
as the orientation depends on the drawing direction. Because the pm3d algorithm does not extend the<br />
colored surface outside the range of the input data points, the ’c’ coloring options will result in pixels<br />
along two edges of the grid not contributing to the color of any quadrangle. For example, applying the<br />
pm3d algorithm to the 4x4 grid of data points in script demo/pm3d.dem (please have a look) produces<br />
only (4-1)x(4-1)=9 colored rectangles.<br />
Another drawing algorithm, which would draw quadrangles around a given node by taking corners from<br />
averaged (x,y)-coordinates of its surrounding 4 nodes while using node’s color, could be implemented in<br />
the future. This is already done for drawing images (2D grids) via image and rgbimage styles.<br />
Notice that ranges of z-values and color-values for surfaces are adjustable independently by set zrange,<br />
set cbrange, as well as set log for z or cb. Maps can be adjusted by the cb-axis only; see also set<br />
view map (p. 139) and set colorbox (p. 93).<br />
The option hidden3d takes as the argument a linestyle which must be created by set style line ....<br />
(The style need not to be present when setting pm3d, but it must be present when plotting). If set, lines<br />
are drawn using the specified line style, taking into account hidden line removal. This is by far more<br />
efficient than using the command set hidden3d as it doesn’t really calculate hidden line removal, but<br />
just draws the filled polygons in the correct order. So the recommended choice when using pm3d is<br />
set pm3d at s hidden3d 100<br />
set style line 100 lt 5 lw 0.5<br />
unset hidden3d<br />
unset surf