Function:ns2sevas

void ns2sevas(float sx, float sy, float sz);

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

/* Global variables */
int vid;                                /* ID for volume render object */
float tr[12];                           /* Transformation matrix */
float ***volume;                        /* The data cube */
int nx, ny, nz;                         /* Data grid dimensions */

float ***initVolume(int nx, int ny, int nz)
/* Allocate memory and initialise a data cube */
{
   float ***volume;
   int i, j, k;

   volume = (float ***)malloc(nx * sizeof(float **));
   if (volume == NULL) {
      fprintf(stderr,"Failed to allocate %ld bytes\n",(long)(nx*sizeof(float **)));
      exit(-1);
   }
   for (i=0;i<nx;i++) {
      volume[i] = (float **)malloc(ny * sizeof(float *));
      if (volume[i] == NULL) {
         fprintf(stderr,"Failed to allocate %ld bytes\n",(long)(nx*sizeof(float *)));
         exit(-1);
      }
      for (j=0;j<ny;j++) {
         volume[i][j] = (float *)malloc(nz * sizeof(float));
         if (volume[i][j] == NULL) {
            fprintf(stderr,"Failed to allocate %ld bytes\n",(long)(nx*sizeof(float)));
            exit(-1);
         }
         for (k=0;k<nz;k++) {
            volume[i][j][k] = 0.0;              /* Initialise */
         }
      }
   }

   return volume;
}

void cb(double *t, int *kc)
/* A dynamic callback */
{
   s2lab("","","","Press <space> to toggle opactiy mode for volume rendering");
   float sx, sy, sz;                    /* Opacity scale factors */

   if (*kc % 2 == 1 ) {
      sx = (float)nz/(float)nx;
      sy = (float)nz/(float)ny;
      sz = 1.0;                         /* Shortest axis gets highest opacity scale */
      ns2sevas(sx,sy,sz);               /* Set the opacity scaling */
   } else {
      ns2sevas(1.,1.,1.);               /* Set the opacity scaling */
   }
   ds2dvr(vid, 1);                      /* Draw the volume render object */
}

int main(int argc, char *argv[])
{
   int i;                                       /* Loop variable */
   float dmin, dmax, amin, amax;                /* Min/max values */
   char trans;                                  /* Transparency mode */
   float x1 = -1.0, x2 = +1.0;                  /* Data range along axes */
   float y1 = -1.0, y2 = +1.0;
   float z1 = -1.0, z2 = +1.0;
   int vi, vj, vk;                              /* Temporary variables */
   float dx, dy, dz;                            /* Temporary variables */
   COLOUR amb = {0.8, 0.8, 0.8};                /* Ambient light */

   srand48((long)time(NULL));                   /* Seed random numbers */

   nx = 40; ny = 40; nz = 10;                   /* Dimensions of data cube */
   volume = initVolume(nx, ny, nz);             /* Allocate memory */

   for (i=0;i<12;i++) {                         /* Set-up transfrom matrix */
      tr[i] = 0.0;
   }
   tr[ 0]  = x1;                                /* Mapping from data cube */
   tr[ 1]  = (x2-x1)/(float)(nx-1.0);           /* to physical coordinates */
   tr[ 4]  = y1;
   tr[ 6]  = (y2-y1)/(float)(ny-1.0);
   tr[ 8]  = z1;
   tr[11]  = (z2-z1)/(float)(nz-1.0);

   dmin = 0.0;                  /* Mininum data value in volume to plot */
   dmax = 2.0;                  /* Maximum data value in volume to plot */
   amin = 0.0;                  /* Minimum alpha channel value */
   amax = 0.8;                  /* Maximum alpha channel value */
   trans = 't';                 /* Transparency type */

   dx = tr[1]*0.5;              /* Offsets for window - voxels are pixel */
   dy = tr[6]*0.5;              /*  centred */
   dz = tr[11]*0.5;

   s2opend("/S2MONO",argc,argv);                        /* Open the display */
   s2swin(x1-dx,x2+dx, y1-dy,y2+dy, z1-dz,z2+dz);       /* Set window coords */
   s2box("BCDE",0,0,"BCDE",0,0,"BCDE",0,0);             /* Draw coord box */

   long N = 5000;

   for (i=0;i<N;i++) {                  /* Create N random (x,y,z) values */
      vi = (int)(drand48()*(nx));
      vj = (int)(drand48()*(ny));
      vk = (int)(drand48()*(nz));

      volume[vi][vj][vk]+=1.0-drand48()*drand48();
                                        /* Give a value to volume */
   }

   s2scir(1000,2000);                   /* Set colour range */
   s2icm("mgreen",1000,2000);           /* Install colour map */
   vid = ns2cvr(volume, nx, ny, nz, 0, nx-1, 0, ny-1, 0, nz-1,
                tr, trans, dmin, dmax, amin, amax);
                                        /* Create the volume render object */

   cs2scb(cb);                          /* Install a dynamic callback */
   ss2srm(SHADE_FLAT);                  /* Set shading type to FLAT */
   ss2sl(amb, 0, NULL, NULL, 0);        /* Ambient lighting only */

   ss2sas(1);                           /* Start the cube spinning */

   s2show(1);                           /* Open the s2plot window */

   return 1;
}