grdview(1) GMT grdview(1)
NAME
grdview - Create 3-D perspective image or surface mesh from a grid
SYNOPSIS
grdview relief_file -Jparameters [ -B[p|s]parameters ] [ -C[cpt]] [
-Gdrapefile | -Ggrd_r -Ggrd_g -Ggrd_b ] [ -I[intensfile|inten-
sity|modifiers] ] [ -Jz|Zparameters ] [ -K ] [ -Nlevel[+gfill] ] [ -O
] [ -P ] [ -Qargs[+m] ] [ -Rwest/east/south/north[/zmin/zmax][+r] ] [
-Ssmooth ] [ -T[s][o[pen]] ] [ -U[stamp] ] [ -Wtypepen ] [ -Xx_off-
set ] [ -Yy_offset ] [ -nflags ] [ -pflags ] [ -ttransp ]
Note: No space is allowed between the option flag and the associated
arguments.
DESCRIPTION
grdview reads a 2-D grid file and produces a 3-D perspective plot by
drawing a mesh, painting a colored/grayshaded surface made up of poly-
gons, or by scanline conversion of these polygons to a raster image.
Options include draping a data set on top of a surface, plotting of
contours on top of the surface, and apply artificial illumination based
on intensities provided in a separate grid file.
REQUIRED ARGUMENTS
relief_file
2-D gridded data set to be imaged (the relief of the surface).
(See GRID FILE FORMAT below.)
-Jparameters (more a|)
Select map projection.
-Jz|Zparameters (more a|)
Set z-axis scaling; same syntax as -Jx.
OPTIONAL ARGUMENTS
-B[p|s]parameters (more a|)
Set map boundary frame and axes attributes.
-C[cpt]
name of the CPT. Must be present if you want (1) mesh plot with
contours (-Qm), or (2) shaded/colored perspective image (-Qs or
-Qi). For -Qs: You can specify that you want to skip a z-slice
by setting the red r/g/b component to -; to use a pattern give
red = P|ppattern[+bcolor][+fcolor][+rdpi]. Alternatively, sup-
ply the name of a GMT color master dynamic CPT [rainbow] to
automatically determine a continuous CPT from the gridas
z-range. If the dynamic CPT has a default range then that range
will be imposed instead.
-Gdrapefile | -Ggrd_r -Ggrd_g -Ggrd_b
Drape the image in drapefile on top of the relief provided by
relief_file. [Default is relief_file]. Note that -Jz and -N
always refers to the relief_file. The drapefile only provides
the information pertaining to colors, which is looked-up via the
CPT (see -C). Alternatively, give three grid files via separate
-G options in the specified order. These files must contain the
red, green, and blue colors directly (in 0-255 range) and no CPT
is needed. The drapefile may be of higher resolution than the
relief_file.
-I[intensfile|intensity|modifiers]
Gives the name of a grid file with intensities in the (-1,+1)
range, or a constant intensity to apply everywhere; this simply
affects the ambient light. If just + is given then we derive an
intensity grid from the input data grid grd_z via a call to grd-
gradient using the arguments -A-45 and -Nt1 for that module. You
can append +aazimuth and **+n*args to override those values. If
you want more specific intensities then run grdgradient sepa-
rately first. [Default is no illumination].
-K (more a|)
Do not finalize the PostScript plot.
-Nlevel[+gfill]
Draws a plane at this z-level. If the optional color is provided
via the +g modifier, the frontal facade between the plane and
the data perimeter is colored. See -Wf for setting the pen used
for the outline.
-O (more a|)
Append to existing PostScript plot.
-P (more a|)
Select aPortraita plot orientation.
-Qargs[+m]
Select one of following settings. For any of these choices, you
may force a monochrome image by appending the modifier +m. Col-
ors are then converted to shades of gray using the (monochrome
television) YIQ transformation
1. Specify m for mesh plot [Default], and optionally append
color for a different mesh paint [white].
2. Specify mx or my for waterfall plots (row or column pro-
files). Specify color as for plain m
3. Specify s for surface plot, and optionally append m to have
mesh lines drawn on top of surface.
4. Specify i for image plot, and optionally append the effective
dpi resolution for the rasterization [100].
5. Specify c. Same as -Qi but will make nodes with z = NaN
transparent, using the colormasking feature in PostScript
Level 3 (the PS device must support PS Level 3). .
-Rxmin/xmax/ymin/ymax[+r][+uunit] (more a|)
Specify the region of interest.
For perspective view p, optionally append /zmin/zmax. (more a|) This
option may be used to indicate the range used for the 3-D axes [Default
is region given by the relief_file]. You may ask for a larger w/e/s/n
region to have more room between the image and the axes. A smaller
region than specified in the relief_file will result in a subset of the
grid.
-Ssmooth
Smooth the contours before plotting (see grdcontour) [Default is
no smoothing].
-T[s][o[pen]]
Plot image without any interpolation. This involves converting
each node-centered bin into a polygon which is then painted sep-
arately. Append s to skip nodes with z = NaN. This option is
useful for categorical data where interpolating between values
is meaningless. Optionally, append o to draw the tile outlines,
and specify a custom pen if the default pen is not to your lik-
ing. As this option produces a flat surface it cannot be com-
bined with -JZ or -Jz.
-U[[just]/dx/dy/][c|label] (more a|)
Draw GMT time stamp logo on plot.
-V[level] (more a|)
Select verbosity level [c].
-Wtypepen
-Wc Draw contour lines on top of surface or mesh (not image).
Append pen attributes used for the contours. [Default: width
= 0.75p, color = black, style = solid].
-Wm Sets the pen attributes used for the mesh. [Default: width =
0.25p, color = black, style = solid]. You must also select
-Qm or -Qsm for meshlines to be drawn.
-Wf Sets the pen attributes used for the facade. [Default: width
= 0.25p, color = black, style = solid]. You must also select
-N for the facade outline to be drawn.
-X[a|c|f|r][x-shift[u]]
-Y[a|c|f|r][y-shift[u]] (more a|)
Shift plot origin.
-n[b|c|l|n][+a][+bBC][+c][+tthreshold] (more a|)
Select interpolation mode for grids.
-p[x|y|z]azim[/elev[/zlevel]][+wlon0/lat0[/z0]][+vx0/y0] (more a|)
Select perspective view.
-t[transp] (more a|)
Set PDF transparency level in percent.
-^ or just -
Print a short message about the syntax of the command, then
exits (NOTE: on Windows just use -).
-+ or just +
Print an extensive usage (help) message, including the explana-
tion of any module-specific option (but not the GMT common
options), then exits.
-? or no arguments
Print a complete usage (help) message, including the explanation
of all options, then exits.
GRID FILE FORMATS
By default GMT writes out grid as single precision floats in a
COARDS-complaint netCDF file format. However, GMT is able to produce
grid files in many other commonly used grid file formats and also
facilitates so called apackinga of grids, writing out floating point
data as 1- or 2-byte integers. (more a|)
CONSEQUENCES OF GRID RESAMPLING
Except for Cartesian cases, we need to resample your geographic grid
onto an equidistant projected grid. In doing so various algorithms come
into play that projects data from one lattice to another while avoiding
anti-aliasing, leading to possible distortions. One expected effect of
resampling with splines is the tendency for the new resampled grid to
slightly exceed the global min/max limits of the original grid. If
this is coupled with tight CPT limits you may find that some map areas
may show up with fore- or background color due to the resampling. In
that case you have two options: (1) Modify your CPT to fit the resam-
pled extrema (reported with -V) or (2) Impose clipping of resampled
values so they do not exceed the input min/max values (add +c to your
-n option).
EXAMPLES
To make a mesh plot from the file hawaii_grav.nc and drawing the con-
tours given in the CPT hawaii.cpt on a Lambert map at 1.5 cm/degree
along the standard parallels 18 and 24, with vertical scale 20 mgal/cm,
and looking at the surface from SW at 30 degree elevation, run
gmt grdview hawaii_grav.nc -Jl18/24/1.5c -Chawaii.cpt \
-Jz0.05c -Qm -N-100 -p225/30 -Wc > hawaii_grav_image.ps
To create a illuminated color perspective plot of the gridded data set
image.nc, using the CPT color.rgb, with linear scaling at 10 cm/x-unit
and tickmarks every 5 units, with intensities provided by the file
intens.nc, and looking from the SE, use
gmt grdview image.nc -Jx10.0c -Ccolor.rgb -Qs -p135/30 -Iintens.nc > image3D.ps
To make the same plot using the rastering option with dpi = 50, use
gmt grdview image.nc -Jx10.0c -Ccolor.rgb -Qi50 -p135/30 -Iintens.nc > image3D.ps
To create a color PostScript perspective plot of the gridded data set
magnetics.nc, using the CPT mag_intens.cpt, draped over the relief
given by the file topography.nc, with Mercator map width of 6 inch and
tickmarks every 1 degree, with intensities provided by the file
topo_intens.nc, and looking from the SE, run
gmt grdview topography.nc -JM6i -Gmagnetics.nc -Cmag_intens.cpt \
-Qs -p140/30 -Itopo_intens.nc > draped3D.ps
Given topo.nc and the Landsat image veggies.ras, first run grd2rgb to
get the red, green, and blue grids, and then drape this image over the
topography and shade the result for good measure. The commands are
gmt grd2rgb veggies.ras -Glayer_%c.nc
gmt grdview topo.nc -JM6i -Qi -p140/30 -Itopo_intens.nc \
-Glayer_r.nc -Glayer_g.nc -Glayer_b.nc > image.ps
REMARKS
For the -Qs option: PostScript provides no way of smoothly varying col-
ors within a polygon, so colors can only vary from polygon to polygon.
To obtain smooth images this way you may resample the grid file(s)
using grdsample or use a finer grid size when running gridding programs
like surface or nearneighbor. Unfortunately, this produces huge Post-
Script files. The alternative is to use the -Qi option, which computes
bilinear or bicubic continuous color variations within polygons by
using scanline conversion to image the polygons.
SEE ALSO
gmt(1), grd2rgb(1), gmtcolors(5), grdcontour(1), grdimage(1),
grdsample(1), nearneighbor(1), psbasemap(1), pscontour(1), pstext(1),
surface(1)
COPYRIGHT
2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
5.4.2 Jun 24, 2017 grdview(1)
gmt5 5.4.2 - Generated Thu Jun 29 08:32:33 CDT 2017