c
c  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
c  .                                                             .
c  .                  copyright (c) 1998 by UCAR                 .
c  .                                                             .
c  .       University Corporation for Atmospheric Research       .
c  .                                                             .
c  .                      all rights reserved                    .
c  .                                                             .
c  .                                                             .
c  .                         SPHEREPACK                          .
c  .                                                             .
c  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
c
c ... visgeo.f
c
c     contains documentation and code for subroutine visgeo
c
c     SUBROUTINE VISGEO (M,IDP,JDP,X,Y,Z,H,EYER,EYELAT,EYELON,
c    1                          WORK,LWORK,IWORK,LIWORK,IERROR)
c
c     subroutine visgeo will display a function on the sphere
c     as a solid. ie. as a "lumpy" sphere. visgeo calls subroutine
c     vsurf to produce the visible surface rendering. X, Y, and Z
c     are the points on an icosahedral geodesic computed by
c     subroutine geopts available in spherepack.
c
c     requires routines visgeo1 ctos stoc vsurf vsurf1
c                       prjct box
c
c     visgeo uses the ncar graphics package.
c     compile with: ncargf77 (all programs above)
c
c     execute with:  a.out
c
c     on screen display with:  ctrans -d x11 gmeta
c                          
c     print with:  ctrans -d ps.color gmeta > gmeta.ps
c                  lpr -P(your printer) gmeta.ps 
c
c
c     input parameters
c
c     m        the number of points on one edge of the icosahedron
c
c     idp,jdp  the first and second dimensions of the three
c              dimensional arrays x, y, z, and h.
c
c     x,y,z    the coordinates of the geodesic points on 
c              the unit sphere computed by subroutine geopts.
c              the indices are defined on the unfolded 
c              icosahedron as follows for the case m=3
c
c                north pole
c
c                 (5,1)          0      l
c        i     (4,1) (5,2)              a    (repeated for
c           (3,1) (4,2) (5,3)  theta1   t    k=2,3,4,5 in
c        (2,1) (3,2) (4,3)              i        -->
c     (1,1) (2,2) (3,3)        theta2   t    the longitudinal 
c        (1,2) (2,3)                    u    direction)
c           (1,3)                pi     d
c      j                                e
c         south pole
c
c            total number of vertices is  10*(m-1)**2+2
c            total number of triangles is 20*(m-1)**2
c
c     h      a three dimensional array that contains the discrete
c            function to be displayed. h(i,j,k) is the distance from
c            the center of the sphere to the "lumpy" surface at the
c             point [x(i,j,k),y(i,j,k),z(i,j,k)] on the unit sphere.
c
c     eyer   the distance from the center of the sphere to the eye.
c
c     eyelat the colatitudinal coordinate of the eye (in degrees).
c
c     eyelon the longitudinal  coordinate of the eye (in degrees).
c
c     idp    the first dimension of the array h as it appears in
c            the program that calls visgeo
c
c     jdp    the second dimension of the array h as it appears in
c            the program that calls visgeo
c
c     work   a real work array 
c
c     lwork  the dimension of the array work as it appears in the
c            program that calls visgeo. lwork must be at least 
c                       480*(m-1)**2.
c
c     iwork  an integer work array
c
c     liwork the dimension of the array iwork as it appears in the
c            program that calls visgeo. liwork must be at least 
c                       140*(m-1)**2.
c
c     input parameter
c
c     ierror = 0    no error
c            = 1    h(i,j,k) is less than zero for some i,j,k.
c            = 2    eyer is less than h(i,j,k) for some i,k,k.
c            = 3    lwork  is less than 480*(m-1)**2
c            = 4    liwork is less than 140*(m-1)**2
c