Function:ns2sisa

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "s2plot.h"

/* Global variabl */
int id;                                         /* ID for isosurface object */

void cb(double *t, int *kc)
{
   static int count = 0;                        /* Count number of times in */
   static float alpha = 0.0;                    /* Isosurface alpha channel */
   int force = 1;                               /* Force redraw of surface */
   float dummy;                                 /* A random number */
   char trans;                                  /* Isosurface transparency */

   if (count == 12) {                           /* About once per half second */
      count = 0;                                /* Reset counter */
      alpha = drand48();                        /* Random alpha channel value */
      dummy = drand48();                        /* Random number */
      if (dummy > 0.6) trans = 't';             /* Select transparency type */
      else if (dummy > 0.3) trans = 's';
      else trans = 'o';
      ns2sisa(id, alpha, trans);                /* Set the new isosurface values */
   } else {
      count++;                                  /* Keep counting */
   }
   ns2dis(id, force);                           /* Draw the isosurface */
}

int main(int argc, char *argv[])
{
   int i, j, k;                         /* Loop variables */
   float x, y, z;                       /* Dummy variables for grid values */
   int nx, ny, nz;                      /* Number of cells in grid */
   float ***grid;                       /* Grid data */
   float tr[12];                        /* Transformation matrix */
   int resolution;                      /* Resolution of isosurface */
   float level;                         /* Isosurface level to plot */
   float alpha;                         /* Alpha channel */
   char trans;                          /* Drawing mode for isosurface */

   nx = 30;                             /* Grid dimensions */
   ny = 30;
   nz = 30;

  /* Create transpose matrix mapping data indices to world coords */
   tr[0] = tr[4] = tr[8] = 0.0;                           /* Offsets */
   tr[1] = tr[6] = tr[11] = 1.0;                          /* Increments */
   tr[2] = tr[3] = tr[5] = tr[7] = tr[9] = tr[10] = 0.;   /* Cross terms */

   s2opend("/?",argc, argv);                    /* Open the display */
   s2swin(0, nx-1, 0, ny-1, 0, nz-1);           /* Set the window coordinates */
   s2box("BCDET",0,0,"BCDET",0,0,"BCDET",0,0);  /* Draw coordinate box */

   /* allocate and generate the data grid */
   grid = (float ***)malloc(nx * sizeof(float **));
   for (i = 0; i < nx; i++) {
      grid[i] = (float **)malloc(ny * sizeof(float *));
      x = (float)(i) / (float)(nx - 1);
      for (j = 0; j < ny; j++) {
         grid[i][j] = (float *)malloc(nz * sizeof(float));
         y = (float)(j) / (float)(ny - 1);
         for (k = 0; k < nz; k++) {
            z = (float)(k) / (float)(nz - 1);
            grid[i][j][k] = x*x*x + y*y - z*z*z*z;
         }
      }
   }
   level      = 0.2;                    /* Set the isosurface level */
   resolution = 1;                      /* Set the isosurface resolution */
   alpha      = 0.0;                    /* Set the alpha channel */
   trans      = 'o';                    /* Opaque isosurface */

/* Create the isosurface object */
   id = ns2cis(grid, nx, ny, nz, 0, nx-1, 0, ny-1, 0, nz-1,
                   tr, level, resolution, trans, alpha, 1., 1., 0.);

   s2scb(&cb);                          /* Install a dynamic callback */
   s2show(1);                           /* Open the s2plot window */

   return 1;
}