This patch will produce a 5 x 5 degree dashed lat-lon grid on any
exisitng worldmap in VIS-5D, with a resolution of the lines at about
1 degree.  If you want a different resolution, some changes in array sizes,
the constants ic and jc, and for-loop sizes will be necessary.

0.  Keep a copy of map.c before altering this (just in case! )
1.  Go to the part of map.c  (in the src directory) where this module is:

-------------------------------

/*
 * Draw the map.
 * Input:  time - time step
 *         flat - 1 = draw flat map
 *                  0 = draw raised map
 * Return:  nothing.
 */
int draw_map( Display_Context dtx, int time, int flat )

-------------------------------
2.  After this point, delete the rest of the module and insert the following:
-------------------------------

{
   int i, nlon, nlat, ic, jc, isgn, s, icc, jcc, idc;

   int ii, im, jm, imln, jmlt, imxln, jmxlt;
   float mlb[2][3];
/*  These array sizes will vary depending upon the resolution you want  */   
   float lonmlb[100];
   float latmlb[100];
   float mlonp[361];
   float mlatp[181];
   float x[361], y[181], z[2];
   float mgt[1];



   if (flat) {
      /* draw a flat map */
      for (i=0;i<dtx->SegCount;i++) {
         polyline( dtx->FlatMapVert+dtx->Start[i], dtx->Len[i] );

      /*  printf("%f\n",dtx->FlatMapVert[0][2]); */
        
      }
   }
   else {
      /* draw a map with heights */
      for (i=0;i<dtx->SegCount;i++) {
         polyline( dtx->MapVert+dtx->Start[i], dtx->Len[i] );
      }
   }
         ic=73;
         for (im=0;im<ic;im++)  {
           lonmlb[im]= -180.+(im)*5.0;
         }

         jc=36;
         for (jm=0;jm<jc;jm++)  {
           latmlb[jm]=-90.+jm*5.0;
         } 
        
    /*    printf("%f %d %d\n",lonmlb[2],jc,ic); */

         for (jcc=0;jcc<jc;jcc++) {
          for (icc=0;icc<360;icc++) {

         /*  printf("%d %d\n",jcc,icc);  */

           mlonp[icc]=-180.+ (float)(icc);

     /*      printf("%f %f %f %f %f %f\n",latmlb[jcc],mlonp[icc],mgt[0],
                   x[icc],y[icc],z[0]);  */

        geo_to_xyzPRIME( dtx,-1, -1, 1,
                &latmlb[jcc], &mlonp[icc],&mgt[0],
                 &x[icc], &y[icc], &z[0] ); 
             if (icc==0 || jcc==0)  {
              s=0;
             }
             else  {
            mlb[0][0]=x[icc-1];
            mlb[0][1]=y[icc-1];

/*  this line keeps the lines in step with the map  */
             mlb[0][2]=dtx->FlatMapVert[0][2];

            mlb[1][0]=x[icc];
            mlb[1][1]=y[icc];
            mlb[1][2]=dtx->FlatMapVert[0][2];
            if (icc % 2 != 0 && x[icc] < 1. && x[icc] > -1.
                            && y[icc] < 1. && y[icc] > -1.) {
                  polyline(mlb,2);
              }
             }
          }
         } 

         for (jcc=0;jcc<ic+1;jcc++) {
       /*  omitting lat lines from +/- 90 to +/- 85 degrees  */
          for (icc=10;icc<350;icc++) {

       /*    printf("%d %d %f\n",jcc,icc,latmlb[jcc]); */

           mlatp[icc]=-90.+(float)(icc)/2.;

      /*     printf("%f %f %f %f %f %f\n",lonmlb[jcc],mlatp[icc],mgt[0],
                  x[icc],y[icc],z[0]);  */

        geo_to_xyzPRIME( dtx,-1, -1, 1,
                &mlatp[icc], &lonmlb[jcc],&mgt[0],
                 &x[icc], &y[icc], &z[0] );
             if (icc==0 || jcc==0)  {
              s=0;
             }
             else  {
            mlb[0][0]=x[icc-1];
            mlb[0][1]=y[icc-1];
            mlb[0][2]=dtx->FlatMapVert[0][2];
            mlb[1][0]=x[icc];
            mlb[1][1]=y[icc];
            mlb[1][2]=dtx->FlatMapVert[0][2];
          if (icc % 2 != 0 && x[icc] < 1. && x[icc] > -1.
                            && y[icc] < 1. && y[icc] > -1.) {
                  polyline(mlb,2);
              }
             }
          }
         }

   return 0;
}

--------------------------

3.  recompile  VIS-5D, and you should be good to go. 
    This isn't the cleanest or fastest code I'm sure; if someone can
    come up with something more efficient, please let me know. 


peace,

Marcus ><+>

marcus@aos.wisc.edu