## NAME

          grdview - Create 3-D perspective grayshaded/colored image or mesh from
          a 2-D grd file

## SYNOPSIS

          grdview relief_file -Jparameters [ -Btickinfo ] [-Ccptfile] [
          -Eview_az/view_el ] [ -Gdrapefile] [ -Iintensfile] [ -K ] [ -L[flags] ]
          [ -Nlevel[/r/g/b]] [ -O ] [ -P ] [ -Qtype ] [
          -Rwest/east/south/north/zmin/zmax[r] ] [ -Ssmooth ] [
          -U[/dx/dy/][label] ] [ -V ] [ -Wtype/pen ] [ -Xx-shift ] [ -Yy-shift ]
          [ -Zzlevel ] [ -ccopies ]

## DESCRIPTION

          grdview reads a 2-D gridded file and produces a 3-D perspective plot
          by drawing a mesh, painting a colored/grayshaded surface made up of
          polygons, or by scanline conversion of these polygons to a
          rasterimage.  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 grd file.

          relief_file
               2-D gridded data set to be imaged (the relief of the surface).

          -J   Selects the map projection. Scale is inch/degree, 1:xxxxx, or
               width in inch (upper case modifier).

               CYLINDRICAL PROJECTIONS:

               -Jclon0/lat0/scale (Cassini)
               -Jjlon0/scale (Miller)
               -Jmscale (Mercator - Greenwich and Equator as origin)
               -Jmlon0/lat0/scale (Mercator - Give meridian and standard
               parallel)
               -Joalon0/lat0/azimuth/scale (Oblique Mercator - point and
               azimuth)
               -Joblon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
               -Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and pole)
               -Jqlon0/scale (Equidistant Cylindrical Projection (Plate Carree))
               -Jtlon0/scale (TM - Transverse Mercator, with Equator as y = 0)
               -Jtlon0/lat0/scale (TM - Transverse Mercator, set origin)
               -Juzone/scale (UTM - Universal Transverse Mercator)
               -Jylon0/lats/scale (Basic Cylindrical Projection)

               AZIMUTHAL PROJECTIONS:

               -Jalon0/lat0/scale (Lambert).
               -Jelon0/lat0/scale (Equidistant).
               -Jflon0/lat0/horizon/scale (Gnomonic).
               -Jglon0/lat0/scale (Orthographic).
               -Jslon0/lat0/scale (General Stereographic)

               CONIC PROJECTIONS:

               -Jblon0/lat0/lat1/lat2/scale (Albers)
               -Jdlon0/lat0/lat1/lat2/scale (Equidistant)
               -Jllon0/lat0/lat1/lat2/scale (Lambert)

               MISCELLANEOUS PROJECTIONS:

               -Jhlon0/scale (Hammer)
               -Jilon0/scale (Sinusoidal)
               -Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
               -Jnlon0/scale (Robinson)
               -Jrlon0/scale (Winkel Tripel)
               -Jvlon0/scale (Van der Grinten)
               -Jwlon0/scale (Mollweide)

               NON-GEOGRAPHICAL PROJECTIONS:

               -Jpscale (Linear projection for polar (theta,r) coordinates)
               -Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and power
               scaling)
               More details can be found in the psbasemap manpages.

          -Jz  Sets the vertical scaling (for 3-D maps).  Same syntax as -Jx.

## OPTIONS

          No space between the option flag and the associated arguments.

          -B   Sets map boundary tickmark intervals. See psbasemap for details.

          -C   name of the color palette file.  Must be present if you want (1)
               mesh plot with contours (-Qm), or (2) shaded/colored perspective
               image (-Qs or -Qi).

          -E   Sets the view point by specifying azimuth and elevation in
               degrees. [Default is 180/90]

          -G   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.

          -I   Gives the name of a grdfile with intensities in the (-1,+1)
               range. [Default is no illumination].

          -K   More PostScript code will be appended later [Default terminates
               the plot system].

          -L   Boundary condition flags may be x or y or xy indicating data is
               periodic in range of x or y or both, or flags may be g indicating
               geographical conditions (x and y are lon and lat).  [Default uses
               "natural" conditions (second partial derivative normal to edge is
               zero).] If no flags are set, use bilinear rather than the default
               bicubic resampling when draping is required.

          -N   Draws a plane at this z-level.  If the optional r/g/b is
               provided, the frontal facade between the plane and the data
               perimeter is colored.

          -O   Selects Overlay plot mode [Default initializes a new plot
               system].

          -P   Selects Portrait plotting mode [GMT Default is Landscape, see
               gmtdefaults to change this].

          -R   west, east, south, and north specify the Region of interest.  To
               specify boundaries in degrees and minutes [and seconds], use the
               dd:mm[:ss] format.  Append r if lower left and upper right map
               coordinates are given instead of wesn.  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.

          -Q   Select one of three settings: 1. Specify m for mesh plot
               [Default], and optionally append /r/g/b for a different mesh
               paint [white].  2. Specify s for surface plot, and optionally
               append m to have mesh lines drawn on top of surface.  3. Specify
               i for image plot, and optionally append the effective dpi
               resolution for the rasterization [100].  This option will apply a
               simple clippath to avoid overwriting the background (since the
               resulting image is rectangular).  Depending on the projection
               this may backfire; if so turn clipping off by using upper case I.
               For any of these choices, you may force a monochrome image by
               appending g.  Colors are then converted to shades of gray using
               the (television) YIQ transformation.

          -S   Smooth the contours before plotting (see grdcontour) [Default is
               no smoothing]

          -U   Draw Unix System time stamp on plot.  User may specify where the
               lower left corner of the stamp should fall on the page relative
               to lower left corner of plot in inch [Default is (-0.75i/-
               0.75i)].  Optionally, append a label, or c (which will plot the
               command string.)

          -V   Selects verbose mode, which will send progress reports to stderr
               [Default runs "silently"].

          -Wc  Draw contour lines on top of surface or mesh (not image).  Append
               pen attributes used for the contours.  [Default: width = 3, color
               = 0/0/0, texture = solid].

          -Wm  Sets the pen attributes used for the mesh. [Default: width = 1,
               color = 0/0/0, texture = solid].  You must also select -Qm or
               -Qsm for meshlines to be drawn.

          -X -Y
               Shift origin of plot by (x-shift,y-shift) inch  [Default is
               (a1i,a1i) for new plots, (0,0) for overlays].  Prepend a for
               absolute coordinates; the default (r) will reset plot origin.

          -Z   Sets the z-level of the basemap [0].

          -c   Specifies the number of plot copies. [Default is 1]

## EXAMPLES

          To make a mesh plot from the file hawaii_grav.grd and drawing the
          contours given in the color palette file hawaii.cpt on a Lambert map
          at 0.5 inch/degree along the standard parallels 18 and 24, with
          vertical scale 50 mgal/inch, and looking at the surface from SW at 30
          degree elevation, try

          grdview hawaii_grav.grd -Jl18/24/0.5i -Chawaii.cpt -Jz0.02i -Qm -N-100
          -E225/30 -Wc > hawaii_grav_image.ps

          To create a illuminated color perspective plot of the gridded data set
          image.grd, using the color palette file color.rgb, with linear scaling
          at 10 inch/x-unit and tickmarks every 5 units, with intensities
          provided by the file intens.grd, and looking from the SE, try

          grdview image.grd -Jx10.0i -Ccolor.rgb -Qs -E135/30 -Iintens.grd  >
          image3D.ps

          To make the same plot using the rastering option with dpi = 50, try

          grdview image.grd -Jx10.0i -Ccolor.rgb -Qi50 -E135/30 -Iintens.grd  >
          image3D.ps

          To create a color PostScript perspective plot of the gridded data set
          magnetics.grd, using the color palette file mag_intens.cpt, draped
          over the relief given by the file topography.grd, with Mercator map
          width of 6 inch and tickmarks every 1 degree, with intensities
          provided by the file topo_intens.grd, and looking from the SE, try

          grdview topography.grd -JM6i -Gmagnetics.grd -Cmag_intens.cpt -Qs
          -E140/30 -Itopo_intens.grd  > draped3D.ps

## BUGS

          For the -Qs option:  PostScript provides no way of smoothly varying
          colors within a polygon, so colors can only vary from polygon to
          polygon.  To obtain smooth images this way you may resample the
          grdfile(s) using grdsample or use a finer grid size when running
          gridding programs like surface or nearneighbor.  Unfortunately, this
          produces huge PostScript 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.
          However, when using -Qi, the -B option is deactivated; plot axes
          separately as a psbasemap overlay.

          Header must be plotted separately using pstext.

## SEE ALSO

          gmt, grdcontour, grdimage, nearneighbor, psbasemap, pscontour, pstext,
          surface