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 ] [ -T[s]
     ] [ -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 perspec-
     tive  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  UNIT/degree,
          1:xxxxx,  or width in UNIT (upper case modifier).  UNIT
          is cm, inch, or m, depending on the  MEASURE_UNIT  set-
          ting in .gmtdefaults, but this can be overridden on the
          command line by  appending  the  c,  i,  or  m  to  the
          scale/width value.

          CYLINDRICAL PROJECTIONS:

          -Jclon0/lat0/scale (Cassini)
          -Jjlon0/scale (Miller)
          -Jmscale (Mercator - Greenwich and Equator as origin)
          -Jmlon0/lat0/scale (Mercator - Give meridian and  stan-
          dard 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  ori-
          gin)
          -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[/origin] (polar (theta,r) coordinates, option-
          ally offset theta [0])
          -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  argu-
     ments.

     -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 dif-
          ferent 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].  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]

     -T   Plot image without any  interpolation.   This  involves
          converting  each node-centered bin into a polygon which
          is then painted separately.  Append  s  to  skip  nodes
          with  z  =  NaN.  This option is useful for categorical
          data where interpolating between values is meaningless.

     -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.
          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).   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  draw-
     ing  the contours given in the color palette file hawaii.cpt
     on a Lambert map at 1.5 cm/degree along the standard  paral-
     lels  18 and 24, with vertical scale 20 mgal/cm, and looking
     at the surface from SW at 30 degree elevation, try

     grdview hawaii_grav.grd -Jl18/24/1.5c -Chawaii.cpt  -Jz0.05c
     -Qm -N-100 -E225/30 -Wc > hawaii_grav_image.ps

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

     grdview  image.grd   -Jx10.0c   -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  -Jx10.0c  -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 tick-
     marks 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 varia-
     tions within polygons by using scanline conversion to  image
     the polygons.


SEE ALSO

     gmt(l),   grdcontour(l),    grdimage(l),    nearneighbor(l),
     psbasemap(l), pscontour(l), pstext(l), surface(l)