local function fade(t)
	return t * t * t * (t * (t * 6 - 15) + 10)
end

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

local function grad(hash, x, y, z)
	local h = hash % 16
	local u, v, r

	if h < 8 then u = x else u = y end
	if h < 4 then v = y elseif h == 12 or h == 14 then v = x else v = z end
	if h % 2 == 0 then r = u else r = -u end
	if h % 4 == 0 then r = r + v else r = r - v end
	return r
end

local perlin = {}
perlin.p = {}
perlin.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
}
perlin.size = 256

function perlin:load()
for i = 0, self.size - 1 do
	self.p[i] = self.permutation[i + 1]
	self.p[self.size + i] = self.p[i]
end
end

function perlin:noise(x, y, z)
	local X = math.floor(x % 255)
	local Y = math.floor(y % 255)
	local Z = math.floor(z % 255)

	x = x - math.floor(x)
	y = y - math.floor(y)
	z = z - math.floor(z)
	local u = fade(x)
	local v = fade(y)
	local w = fade(z)
	local A  = self.p[X] + Y
	local AA = self.p[A] + Z
	local AB = self.p[A + 1] + Z
	local B  = self.p[X + 1] + Y
	local BA = self.p[B] + Z
	local BB = self.p[B + 1] + Z
	return lerp(w, 	lerp(v, lerp(u,	grad(self.p[AA  ], x  , y  , z  ),
									grad(self.p[BA  ], x-1, y  , z  )),
							lerp(u, grad(self.p[AB  ], x  , y-1, z  ),
									grad(self.p[BB  ], x-1, y-1, z  ))),
							lerp(v, lerp(u, grad(self.p[AA+1], x  , y  , z-1),
									grad(self.p[BA+1], x-1, y  , z-1)),
							lerp(u, grad(self.p[AB+1], x  , y-1, z-1),
									grad(self.p[BB+1], x-1, y-1, z-1))))
end

return perlin