2 Implemented as described here:
3 http://flafla2.github.io/2014/08/09/perlinnoise.html
9 -- Hash lookup table as defined by Ken Perlin
10 -- This is a randomly arranged array of all numbers from 0-255 inclusive
11 local permutation = {151,160,137,91,90,15,
12 131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
13 190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
14 88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
15 77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
16 102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
17 135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
18 5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
19 223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
20 129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
21 251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
22 49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
23 138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
26 -- p is used to hash unit cube coordinates to [0, 255]
28 -- Convert to 0 based index table
29 perlin.p[i] = permutation[i+1]
30 -- Repeat the array to avoid buffer overflow in hash function
31 perlin.p[i+256] = permutation[i+1]
34 -- Return range: [-1, 1]
35 function perlin:noise(x, y, z)
39 -- Calculate the "unit cube" that the point asked will be located in
40 local xi = bit32.band(math.floor(x),255)
41 local yi = bit32.band(math.floor(y),255)
42 local zi = bit32.band(math.floor(z),255)
44 -- Next we calculate the location (from 0 to 1) in that cube
49 -- We also fade the location to smooth the result
50 local u = self.fade(x)
51 local v = self.fade(y)
52 local w = self.fade(z)
54 -- Hash all 8 unit cube coordinates surrounding input coordinate
56 local A, AA, AB, AAA, ABA, AAB, ABB, B, BA, BB, BAA, BBA, BAB, BBB
73 -- Take the weighted average between all 8 unit cube coordinates
78 self:grad(BAA,x-1,y,z)
81 self:grad(ABA,x,y-1,z),
82 self:grad(BBA,x-1,y-1,z)
87 self:grad(AAB,x,y,z-1), self:grad(BAB,x-1,y,z-1)
90 self:grad(ABB,x,y-1,z-1), self:grad(BBB,x-1,y-1,z-1)
96 -- Gradient function finds dot product between pseudorandom gradient vector
97 -- and the vector from input coordinate to a unit cube vertex
98 perlin.dot_product = {
99 [0x0]=function(x,y,z) return x + y end,
100 [0x1]=function(x,y,z) return -x + y end,
101 [0x2]=function(x,y,z) return x - y end,
102 [0x3]=function(x,y,z) return -x - y end,
103 [0x4]=function(x,y,z) return x + z end,
104 [0x5]=function(x,y,z) return -x + z end,
105 [0x6]=function(x,y,z) return x - z end,
106 [0x7]=function(x,y,z) return -x - z end,
107 [0x8]=function(x,y,z) return y + z end,
108 [0x9]=function(x,y,z) return -y + z end,
109 [0xA]=function(x,y,z) return y - z end,
110 [0xB]=function(x,y,z) return -y - z end,
111 [0xC]=function(x,y,z) return y + x end,
112 [0xD]=function(x,y,z) return -y + z end,
113 [0xE]=function(x,y,z) return y - x end,
114 [0xF]=function(x,y,z) return -y - z end
116 function perlin:grad(hash, x, y, z)
117 return self.dot_product[bit32.band(hash,0xF)](x,y,z)
120 -- Fade function is used to smooth final output
121 function perlin.fade(t)
122 return t * t * t * (t * (t * 6 - 15) + 10)
125 function perlin.lerp(t, a, b)
126 return a + t * (b - a)