fractalnoise.c

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#include "quakedef.h"
 
void fractalnoise(unsigned char *noise, int size, int startgrid)
{
    int x, y, g, g2, amplitude, min, max, size1 = size - 1, sizepower, gridpower;
    int *noisebuf;
#define n(x,y) noisebuf[((y)&size1)*size+((x)&size1)]
 
    for (sizepower = 0;(1 << sizepower) < size;sizepower++);
    if (size != (1 << sizepower))
    {
        Con_Printf("fractalnoise: size must be power of 2\n");
        return;
    }
 
    for (gridpower = 0;(1 << gridpower) < startgrid;gridpower++);
    if (startgrid != (1 << gridpower))
    {
        Con_Printf("fractalnoise: grid must be power of 2\n");
        return;
    }
 
    startgrid = bound(0, startgrid, size);
 
    amplitude = 0xFFFF; // this gets halved before use
    noisebuf = (int *)Mem_Alloc(tempmempool, size*size*sizeof(int));
    memset(noisebuf, 0, size*size*sizeof(int));
 
    for (g2 = startgrid;g2;g2 >>= 1)
    {
        // brownian motion (at every smaller level there is random behavior)
        amplitude >>= 1;
        for (y = 0;y < size;y += g2)
            for (x = 0;x < size;x += g2)
                n(x,y) += (rand()&amplitude);
 
        g = g2 >> 1;
        if (g)
        {
            // subdivide, diamond-square algorithm (really this has little to do with squares)
            // diamond
            for (y = 0;y < size;y += g2)
                for (x = 0;x < size;x += g2)
                    n(x+g,y+g) = (n(x,y) + n(x+g2,y) + n(x,y+g2) + n(x+g2,y+g2)) >> 2;
            // square
            for (y = 0;y < size;y += g2)
                for (x = 0;x < size;x += g2)
                {
                    n(x+g,y) = (n(x,y) + n(x+g2,y) + n(x+g,y-g) + n(x+g,y+g)) >> 2;
                    n(x,y+g) = (n(x,y) + n(x,y+g2) + n(x-g,y+g) + n(x+g,y+g)) >> 2;
                }
        }
    }
    // find range of noise values
    min = max = 0;
    for (y = 0;y < size;y++)
        for (x = 0;x < size;x++)
        {
            if (n(x,y) < min) min = n(x,y);
            if (n(x,y) > max) max = n(x,y);
        }
    max -= min;
    max++;
    // normalize noise and copy to output
    for (y = 0;y < size;y++)
        for (x = 0;x < size;x++)
            *noise++ = (unsigned char) (((n(x,y) - min) * 256) / max);
    Mem_Free(noisebuf);
#undef n
}
 
// unnormalized, used for explosions mainly, does not allocate/free memory (hence the name quick)
void fractalnoisequick(unsigned char *noise, int size, int startgrid)
{
    int x, y, g, g2, amplitude, size1 = size - 1, sizepower, gridpower;
#define n(x,y) noise[((y)&size1)*size+((x)&size1)]
 
    for (sizepower = 0;(1 << sizepower) < size;sizepower++);
    if (size != (1 << sizepower))
    {
        Con_Printf("fractalnoise: size must be power of 2\n");
        return;
    }
 
    for (gridpower = 0;(1 << gridpower) < startgrid;gridpower++);
    if (startgrid != (1 << gridpower))
    {
        Con_Printf("fractalnoise: grid must be power of 2\n");
        return;
    }
 
    startgrid = bound(0, startgrid, size);
 
    amplitude = 255; // this gets halved before use
    memset(noise, 0, size*size);
 
    for (g2 = startgrid;g2;g2 >>= 1)
    {
        // brownian motion (at every smaller level there is random behavior)
        amplitude >>= 1;
        for (y = 0;y < size;y += g2)
            for (x = 0;x < size;x += g2)
                n(x,y) += (rand()&amplitude);
 
        g = g2 >> 1;
        if (g)
        {
            // subdivide, diamond-square algorithm (really this has little to do with squares)
            // diamond
            for (y = 0;y < size;y += g2)
                for (x = 0;x < size;x += g2)
                    n(x+g,y+g) = (unsigned char) (((int) n(x,y) + (int) n(x+g2,y) + (int) n(x,y+g2) + (int) n(x+g2,y+g2)) >> 2);
            // square
            for (y = 0;y < size;y += g2)
                for (x = 0;x < size;x += g2)
                {
                    n(x+g,y) = (unsigned char) (((int) n(x,y) + (int) n(x+g2,y) + (int) n(x+g,y-g) + (int) n(x+g,y+g)) >> 2);
                    n(x,y+g) = (unsigned char) (((int) n(x,y) + (int) n(x,y+g2) + (int) n(x-g,y+g) + (int) n(x+g,y+g)) >> 2);
                }
        }
    }
#undef n
}
 
#define NOISE_SIZE 256
#define NOISE_MASK 255
float noise4f(float x, float y, float z, float w)
{
    int i;
    int index[4][2];
    float frac[4][2];
    float v[4];
    static float noisetable[NOISE_SIZE];
    static int r[NOISE_SIZE];
    // LadyHavoc: this is inspired by code I saw in Quake3, however I think my
    // version is much cleaner and substantially faster as well
    //
    // the following changes were made:
    // 1. for the permutation indexing (r[] array in this code) I substituted
    //    the ^ operator (which never overflows) for the original addition and
    //    masking code, this should not have any effect on quality.
    // 2. removed the outermost randomization array lookup.
    //    (it really wasn't necessary, it's fine if X indexes the array
    //     directly without permutation indexing)
    // 3. reimplemented the blending using frac[] arrays rather than a macro.
    //    (the original macro read one parameter twice - not good)
    // 4. cleaned up the code by using 4 nested loops to make it read nicer
    //    (but then I unrolled it completely for speed, it still looks nicer).
    if (!noisetable[0])
    {
        // noisetable is a random-ish series of float values in +/- 1 range
        for (i = 0;i < NOISE_SIZE;i++)
            noisetable[i] = (rand() / (double)RAND_MAX) * 2 - 1;
        // r is a remapping table to make each dimension of the index have different indexing behavior
        for (i = 0;i < NOISE_SIZE;i++)
            r[i] = (int)(rand() * (double)NOISE_SIZE / ((double)RAND_MAX + 1)) & NOISE_MASK;
            // that & is only needed if RAND_MAX is > the range of double, which isn't the case on most platforms
    }
    frac[0][1] = x - floor(x);index[0][0] = ((int)floor(x)) & NOISE_MASK;
    frac[1][1] = y - floor(y);index[1][0] = ((int)floor(y)) & NOISE_MASK;
    frac[2][1] = z - floor(z);index[2][0] = ((int)floor(z)) & NOISE_MASK;
    frac[3][1] = w - floor(w);index[3][0] = ((int)floor(w)) & NOISE_MASK;
    for (i = 0;i < 4;i++)
        frac[i][0] = 1 - frac[i][1];
    for (i = 0;i < 4;i++)
        index[i][1] = (index[i][0] < NOISE_SIZE - 1) ? (index[i][0] + 1) : 0;
#if 1
    // short version
    v[0] = frac[1][0] * (frac[0][0] * noisetable[r[r[r[index[3][0]] ^ index[2][0]] ^ index[1][0]] ^ index[0][0]] + frac[0][1] * noisetable[r[r[r[index[3][0]] ^ index[2][0]] ^ index[1][0]] ^ index[0][1]]) + frac[1][1] * (frac[0][0] * noisetable[r[r[r[index[3][0]] ^ index[2][0]] ^ index[1][1]] ^ index[0][0]] + frac[0][1] * noisetable[r[r[r[index[3][0]] ^ index[2][0]] ^ index[1][1]] ^ index[0][1]]);
    v[1] = frac[1][0] * (frac[0][0] * noisetable[r[r[r[index[3][0]] ^ index[2][1]] ^ index[1][0]] ^ index[0][0]] + frac[0][1] * noisetable[r[r[r[index[3][0]] ^ index[2][1]] ^ index[1][0]] ^ index[0][1]]) + frac[1][1] * (frac[0][0] * noisetable[r[r[r[index[3][0]] ^ index[2][1]] ^ index[1][1]] ^ index[0][0]] + frac[0][1] * noisetable[r[r[r[index[3][0]] ^ index[2][1]] ^ index[1][1]] ^ index[0][1]]);
    v[2] = frac[1][0] * (frac[0][0] * noisetable[r[r[r[index[3][1]] ^ index[2][0]] ^ index[1][0]] ^ index[0][0]] + frac[0][1] * noisetable[r[r[r[index[3][1]] ^ index[2][0]] ^ index[1][0]] ^ index[0][1]]) + frac[1][1] * (frac[0][0] * noisetable[r[r[r[index[3][1]] ^ index[2][0]] ^ index[1][1]] ^ index[0][0]] + frac[0][1] * noisetable[r[r[r[index[3][1]] ^ index[2][0]] ^ index[1][1]] ^ index[0][1]]);
    v[3] = frac[1][0] * (frac[0][0] * noisetable[r[r[r[index[3][1]] ^ index[2][1]] ^ index[1][0]] ^ index[0][0]] + frac[0][1] * noisetable[r[r[r[index[3][1]] ^ index[2][1]] ^ index[1][0]] ^ index[0][1]]) + frac[1][1] * (frac[0][0] * noisetable[r[r[r[index[3][1]] ^ index[2][1]] ^ index[1][1]] ^ index[0][0]] + frac[0][1] * noisetable[r[r[r[index[3][1]] ^ index[2][1]] ^ index[1][1]] ^ index[0][1]]);
    return frac[3][0] * (frac[2][0] * v[0] + frac[2][1] * v[1]) + frac[3][1] * (frac[2][0] * v[2] + frac[2][1] * v[3]);
#elif 1
    // longer version
    v[ 0] = noisetable[r[r[r[index[3][0]] ^ index[2][0]] ^ index[1][0]] ^ index[0][0]];
    v[ 1] = noisetable[r[r[r[index[3][0]] ^ index[2][0]] ^ index[1][0]] ^ index[0][1]];
    v[ 2] = noisetable[r[r[r[index[3][0]] ^ index[2][0]] ^ index[1][1]] ^ index[0][0]];
    v[ 3] = noisetable[r[r[r[index[3][0]] ^ index[2][0]] ^ index[1][1]] ^ index[0][1]];
    v[ 4] = noisetable[r[r[r[index[3][0]] ^ index[2][1]] ^ index[1][0]] ^ index[0][0]];
    v[ 5] = noisetable[r[r[r[index[3][0]] ^ index[2][1]] ^ index[1][0]] ^ index[0][1]];
    v[ 6] = noisetable[r[r[r[index[3][0]] ^ index[2][1]] ^ index[1][1]] ^ index[0][0]];
    v[ 7] = noisetable[r[r[r[index[3][0]] ^ index[2][1]] ^ index[1][1]] ^ index[0][1]];
    v[ 8] = noisetable[r[r[r[index[3][1]] ^ index[2][0]] ^ index[1][0]] ^ index[0][0]];
    v[ 9] = noisetable[r[r[r[index[3][1]] ^ index[2][0]] ^ index[1][0]] ^ index[0][1]];
    v[10] = noisetable[r[r[r[index[3][1]] ^ index[2][0]] ^ index[1][1]] ^ index[0][0]];
    v[11] = noisetable[r[r[r[index[3][1]] ^ index[2][0]] ^ index[1][1]] ^ index[0][1]];
    v[12] = noisetable[r[r[r[index[3][1]] ^ index[2][1]] ^ index[1][0]] ^ index[0][0]];
    v[13] = noisetable[r[r[r[index[3][1]] ^ index[2][1]] ^ index[1][0]] ^ index[0][1]];
    v[14] = noisetable[r[r[r[index[3][1]] ^ index[2][1]] ^ index[1][1]] ^ index[0][0]];
    v[15] = noisetable[r[r[r[index[3][1]] ^ index[2][1]] ^ index[1][1]] ^ index[0][1]];
    v[16] = frac[0][0] * v[ 0] + frac[0][1] * v[ 1];
    v[17] = frac[0][0] * v[ 2] + frac[0][1] * v[ 3];
    v[18] = frac[0][0] * v[ 4] + frac[0][1] * v[ 5];
    v[19] = frac[0][0] * v[ 6] + frac[0][1] * v[ 7];
    v[20] = frac[0][0] * v[ 8] + frac[0][1] * v[ 9];
    v[21] = frac[0][0] * v[10] + frac[0][1] * v[11];
    v[22] = frac[0][0] * v[12] + frac[0][1] * v[13];
    v[23] = frac[0][0] * v[14] + frac[0][1] * v[15];
    v[24] = frac[1][0] * v[16] + frac[1][1] * v[17];
    v[25] = frac[1][0] * v[18] + frac[1][1] * v[19];
    v[26] = frac[1][0] * v[20] + frac[1][1] * v[21];
    v[27] = frac[1][0] * v[22] + frac[1][1] * v[23];
    v[28] = frac[2][0] * v[24] + frac[2][1] * v[25];
    v[29] = frac[2][0] * v[26] + frac[2][1] * v[27];
    return frac[3][0] * v[28] + frac[3][1] * v[29];
#else
    // the algorithm...
    for (l = 0;l < 2;l++)
    {
        for (k = 0;k < 2;k++)
        {
            for (j = 0;j < 2;j++)
            {
                for (i = 0;i < 2;i++)
                    v[l][k][j][i] = noisetable[r[r[r[index[l][3]] ^ index[k][2]] ^ index[j][1]] ^ index[i][0]];
                v[l][k][j][2] = frac[0][0] * v[l][k][j][0] + frac[0][1] * v[l][k][j][1];
            }
            v[l][k][2][2] = frac[1][0] * v[l][k][0][2] + frac[1][1] * v[l][k][1][2];
        }
        v[l][2][2][2] = frac[2][0] * v[l][0][2][2] + frac[2][1] * v[l][1][2][2];
    }
    v[2][2][2][2] = frac[3][0] * v[0][2][2][2] + frac[3][1] * v[1][2][2][2];
#endif
}