Task: Perlin noise

C: #include<stdlib.h>
#include<stdio.h>
#include<math.h>

int p[512];

double fade(double t) { return t * t * t * (t * (t * 6 - 15) + 10); }
double lerp(double t, double a, double b) { return a + t * (b - a); }
double grad(int hash, double x, double y, double z) {
      int h = hash & 15;                      
      double u = h<8 ? x : y,                 
             v = h<4 ? y : h==12||h==14 ? x : z;
      return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
   }
   
double noise(double x, double y, double z) {
      int X = (int)floor(x) & 255,                  
          Y = (int)floor(y) & 255,                  
          Z = (int)floor(z) & 255;
      x -= floor(x);                                
      y -= floor(y);                                
      z -= floor(z);
      double u = fade(x),                                
             v = fade(y),                                
             w = fade(z);
      int A = p[X  ]+Y, AA = p[A]+Z, AB = p[A+1]+Z,      
          B = p[X+1]+Y, BA = p[B]+Z, BB = p[B+1]+Z;   
 
      return lerp(w, lerp(v, lerp(u, grad(p[AA  ], x  , y  , z   ), 
                                     grad(p[BA  ], x-1, y  , z   )),
                             lerp(u, grad(p[AB  ], x  , y-1, z   ), 
                                     grad(p[BB  ], x-1, y-1, z   ))),
                     lerp(v, lerp(u, grad(p[AA+1], x  , y  , z-1 ), 
                                     grad(p[BA+1], x-1, y  , z-1 )), 
                             lerp(u, grad(p[AB+1], x  , y-1, z-1 ),
                                     grad(p[BB+1], x-1, y-1, z-1 ))));
   }

void loadPermutation(char* fileName){
	FILE* fp = fopen(fileName,"r");
	int permutation[256],i;
	
	for(i=0;i<256;i++)
		fscanf(fp,"%d",&permutation[i]);
	
	fclose(fp);
	
	for (int i=0; i < 256 ; i++) p[256+i] = p[i] = permutation[i];
}

int main(int argC,char* argV[])
{
	if(argC!=5)
		printf("Usage : %s <permutation data file> <x,y,z co-ordinates separated by space>");
	else{
		loadPermutation(argV[1]);
		printf("Perlin Noise for (%s,%s,%s) is %.17lf",argV[2],argV[3],argV[4],noise(strtod(argV[2],NULL),strtod(argV[3],NULL),strtod(argV[4],NULL)));
	}
	
	return 0;
}










Fortran: PROGRAM PERLIN
IMPLICIT NONE
INTEGER :: i
INTEGER, DIMENSION(0:511) :: p
INTEGER, DIMENSION(0:255), PARAMETER :: permutation = (/151,160,137,91,90,15,    &
    131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23, &
    190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33, &
    88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166, &
    77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244, &
    102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196, &
    135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123, &
    5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42, &
    223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9, &
    129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228, &
    251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107, &
    49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254, &
    138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180/)

DO i=0, 255
    p(i) = permutation(i)
    p(256+i) = permutation(i)
END DO

WRITE(*,"(F19.17)") NOISE(3.14d0, 42d0, 7d0)

CONTAINS

DOUBLE PRECISION FUNCTION NOISE(x_in, y_in, z_in)
    DOUBLE PRECISION, INTENT(IN) :: x_in, y_in, z_in
    DOUBLE PRECISION :: x, y, z
    INTEGER :: xx, yy, zz, a, aa, ab, b, ba, bb
    DOUBLE PRECISION :: u, v, w

    x = x_in
    y = y_in
    z = z_in

    xx = IAND(FLOOR(x), 255)
    yy = IAND(FLOOR(y), 255)
    zz = IAND(FLOOR(z), 255)

    x = x - FLOOR(x)
    y = y - FLOOR(y)
    z = z - FLOOR(z)

    u = FADE(x)
    v = FADE(y)
    w = FADE(z)

    a  = p(xx)   + yy
    aa = p(a)    + zz
    ab = p(a+1)  + zz
    b  = p(xx+1) + yy
    ba = p(b)    + zz
    bb = p(b+1)  + zz

    NOISE = LERP(w, LERP(v, LERP(u, GRAD(p(aa),   x,   y,   z),     &
                                    GRAD(p(ba),   x-1, y,   z)),    &
                            LERP(u, GRAD(p(ab),   x,   y-1, z),     &
                                    GRAD(p(bb),   x-1, y-1, z))),   &
                    LERP(v, LERP(u, GRAD(p(aa+1), x,   y,   z-1),   &
                                    GRAD(p(ba+1), x-1, y,   z-1)),  &
                            LERP(u, GRAD(p(ab+1), x,   y-1, z-1),   &
                                    GRAD(p(bb+1), x-1, y-1, z-1))))
END FUNCTION


DOUBLE PRECISION FUNCTION FADE(t)
    DOUBLE PRECISION, INTENT(IN) :: t

    FADE = t ** 3 * (t * ( t * 6 - 15) + 10)
END FUNCTION


DOUBLE PRECISION FUNCTION LERP(t, a, b)
    DOUBLE PRECISION, INTENT(IN) :: t, a, b

    LERP = a + t * (b - a)
END FUNCTION


DOUBLE PRECISION FUNCTION GRAD(hash, x, y, z)
    INTEGER, INTENT(IN) :: hash
    DOUBLE PRECISION, INTENT(IN) :: x, y, z
    INTEGER :: h
    DOUBLE PRECISION :: u, v

    h = IAND(hash, 15)

    u = MERGE(x, y, h < 8)

    v = MERGE(y, MERGE(x, z, h == 12 .OR. h == 14), h < 4)

    GRAD = MERGE(u, -u, IAND(h, 1) == 0) + MERGE(v, -v, IAND(h, 2) == 0)
END FUNCTION


END PROGRAM