Perlin Noise in Lua

perlin.lua

--[[
    Implemented as described here:
    http://flafla2.github.io/2014/08/09/perlinnoise.html
]]--

perlin = {}
perlin.p = {}

-- Hash lookup table as defined by Ken Perlin
-- This is a randomly arranged array of all numbers from 0-255 inclusive
local 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
}

-- p is used to hash unit cube coordinates to [0, 255]
for i=0,255 do
    -- Convert to 0 based index table
    perlin.p[i] = permutation[i+1]
    -- Repeat the array to avoid buffer overflow in hash function
    perlin.p[i+256] = permutation[i+1]
end

-- Return range: [-1, 1]
function perlin:noise(x, y, z)
    y = y or 0
    z = z or 0

    -- Calculate the "unit cube" that the point asked will be located in
    local xi = bit32.band(math.floor(x),255)
    local yi = bit32.band(math.floor(y),255)
    local zi = bit32.band(math.floor(z),255)

    -- Next we calculate the location (from 0 to 1) in that cube
    x = x - math.floor(x)
    y = y - math.floor(y)
    z = z - math.floor(z)

    -- We also fade the location to smooth the result
    local u = self.fade(x)
    local v = self.fade(y)
    local w = self.fade(z)

    -- Hash all 8 unit cube coordinates surrounding input coordinate
    local p = self.p
    local A, AA, AB, AAA, ABA, AAB, ABB, B, BA, BB, BAA, BBA, BAB, BBB
    A   = p[xi  ] + yi
    AA  = p[A   ] + zi
    AB  = p[A+1 ] + zi
    AAA = p[ AA ]
    ABA = p[ AB ]
    AAB = p[ AA+1 ]
    ABB = p[ AB+1 ]

    B   = p[xi+1] + yi
    BA  = p[B   ] + zi
    BB  = p[B+1 ] + zi
    BAA = p[ BA ]
    BBA = p[ BB ]
    BAB = p[ BA+1 ]
    BBB = p[ BB+1 ]

    -- Take the weighted average between all 8 unit cube coordinates
    return self.lerp(w,
        self.lerp(v,
            self.lerp(u,
                self:grad(AAA,x,y,z),
                self:grad(BAA,x-1,y,z)
            ),
            self.lerp(u,
                self:grad(ABA,x,y-1,z),
                self:grad(BBA,x-1,y-1,z)
            )
        ),
        self.lerp(v,
            self.lerp(u,
                self:grad(AAB,x,y,z-1), self:grad(BAB,x-1,y,z-1)
            ),
            self.lerp(u,
                self:grad(ABB,x,y-1,z-1), self:grad(BBB,x-1,y-1,z-1)
            )
        )
    )
end

-- Gradient function finds dot product between pseudorandom gradient vector
-- and the vector from input coordinate to a unit cube vertex
perlin.dot_product = {
    [0x0]=function(x,y,z) return  x + y end,
    [0x1]=function(x,y,z) return -x + y end,
    [0x2]=function(x,y,z) return  x - y end,
    [0x3]=function(x,y,z) return -x - y end,
    [0x4]=function(x,y,z) return  x + z end,
    [0x5]=function(x,y,z) return -x + z end,
    [0x6]=function(x,y,z) return  x - z end,
    [0x7]=function(x,y,z) return -x - z end,
    [0x8]=function(x,y,z) return  y + z end,
    [0x9]=function(x,y,z) return -y + z end,
    [0xA]=function(x,y,z) return  y - z end,
    [0xB]=function(x,y,z) return -y - z end,
    [0xC]=function(x,y,z) return  y + x end,
    [0xD]=function(x,y,z) return -y + z end,
    [0xE]=function(x,y,z) return  y - x end,
    [0xF]=function(x,y,z) return -y - z end
}
function perlin:grad(hash, x, y, z)
    return self.dot_product[bit32.band(hash,0xF)](x,y,z)
end

-- Fade function is used to smooth final output
function perlin.fade(t)
    return t * t * t * (t * (t * 6 - 15) + 10)
end

function perlin.lerp(t, a, b)
    return a + t * (b - a)
end

@ryanzec Apologies, I hadn't seen your comment until today. For any future readers:

Feel free to use this code in any project commercial/uncommercial with/without attribution.

Sorry to bug you more about this, but your "permission" is not a license that would fly with FOSS projects. Would you mind specifying something like BSD0 (which most closely matches your permission statement), or MIT, or some Free and Open source license, so that we can use this in FOSS projects?

Having a legally-accepted license statement makes this code actually usable.