# Example 1 - a simple 3D interpolation (C single precision)

```#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <ncarg/ncargC.h>
#include <ncarg/gks.h>
#include <ncarg/ngmath.h>

#define NUM 1000
#define NX    21
#define NY    21
#define NZ    21
#define IWTYPE 1
#define WKID   1

main()
{
int  i, j, k, ier;
float xi[NUM], yi[NUM], zi[NUM], u[NUM];
float xo[NX], yo[NY], zo[NZ], *output, outr[NZ][NY][NX];
float xmin = -2.0, ymin = -2.0, zmin = -2.0;
float xmax =  2.0, ymax =  2.0, zmax =  2.0;

/*
*  Create random data in three space and define a function.
*/
for (i = 0; i < NUM; i++) {
xi[i] = xmin+(xmax-xmin)*((float) rand() / (float) RAND_MAX);
yi[i] = ymin+(ymax-ymin)*((float) rand() / (float) RAND_MAX);
zi[i] = zmin+(zmax-zmin)*((float) rand() / (float) RAND_MAX);
u[i] = xi[i]*xi[i] + yi[i]*yi[i] + zi[i]*zi[i];
}

/*
*  Create the output grid.
*/
for (i = 0; i < NX; i++) {
xo[i] = xmin + ( (float) i / (float) (NX-1)) * (xmax-xmin);
}
for (j = 0; j < NY; j++) {
yo[j] = ymin + ( (float) j / (float) (NY-1)) * (ymax-ymin);
}
for (k = 0; k < NZ; k++) {
zo[k] = zmin + ( (float) k / (float) (NZ-1)) * (zmax-zmin);
}

/*
*  Interpolate.
*/
output = c_dsgrid3s(NUM, xi, yi, zi, u, NX, NY, NZ, xo, yo, zo, &ier);
if (ier != 0) {
printf(" Error %d returned from c_dsgrid3s\n",ier);
exit(1);
}

/*
*  Plot an isosurface.
*/
gopen_gks ("stdout",0);
gopen_ws (WKID, NULL, IWTYPE);
gactivate_ws(WKID);

/*
*  Reorder the array elements for c_tdez3d, since c_dsgrid3s
*  returns an array in column dominate order.
*/
for (i = 0; i < NX; i++) {
for (j = 0; j < NY; j++) {
for (k = 0; k < NZ; k++) {
outr[k][j][i] = output[i*NY*NZ + j*NY + k];
}
}
}
c_tdez3d(NX, NY, NZ, xo, yo, zo, &outr[0][0][0], 3.0, 2., -35., 65., 6);
c_frame();

gdeactivate_ws(WKID);
gclose_ws(WKID);
gclose_gks();
}
```

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