#include "proctext.h"
#include "noise.h"

static float valueTab[TABSIZE];

static void valueTabInit(int seed);
static float vlattice(int ix, int iy, int iz);

float
vnoise(float x, float y, float z)
{
    int ix, iy, iz;
    int i, j, k;
    float fx, fy, fz;
    float xknots[4], yknots[4], zknots[4];
    static int initialized = 0;

    if (!initialized) {
        valueTabInit(665);
        initialized = 1;
    }

    ix = FLOOR(x);
    fx = x - ix;

    iy = FLOOR(y);
    fy = y - iy;

    iz = FLOOR(z);
    fz = z - iz;

    for (k = -1; k <= 2; k++) {
        for (j = -1; j <= 2; j++) {
            for (i = -1; i <= 2; i++)
                xknots[i+1] = vlattice(ix+i,iy+j,iz+k);
            yknots[j+1] = spline(fx, 4, xknots);
        }
        zknots[k+1] = spline(fy, 4, yknots);
    }
    return spline(fz, 4, zknots);
}

static void
valueTabInit(int seed)
{
    float *table = valueTab;
    int i;

    srandom(seed);
    for(i = 0; i < TABSIZE; i++)
        *table++ = 1. - 2.*RANDNBR;
}

static float
vlattice(int ix, int iy, int iz)
{
    return valueTab[INDEX(ix,iy,iz)];
}