noisy/noise.go at master · akmonengine/noisy · GitHub

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package noisy

import (
	"math"
)

var p [512]int
var permutation = []int{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}

func init() {
	for i := 0; i < 256; i++ {
		p[256+i] = permutation[i]
		p[i] = permutation[i]
	}
}

func fade(t float64) float64 {
	return t * t * t * (t*(t*6-15) + 10)
}

func lerp(t, a, b float64) float64 {
	return a + t*(b-a)
}

func grad(hash int, x, y, z float64) float64 {
	h := hash & 15
	var u, v float64
	if h < 8 {
		u = x
	} else {
		u = y
	}
	if h < 4 {
		v = y
	} else if h == 12 || h == 14 {
		v = x
	} else {
		v = z
	}
	var res float64
	if h&1 == 0 {
		res = u
	} else {
		res = -u
	}
	if h&2 == 0 {
		res += v
	} else {
		res -= v
	}
	return res
}

func getNoise(seed int, x, y, z float64) float64 {
	hashValue := uint32(seed)*1664525 + 640406589
	x += float64(hashValue & 0xFF)
	y += float64(hashValue >> 8 & 0xFF)
	z += float64(hashValue >> 16 & 0xFF)

	X := int(math.Floor(x)) & 255
	Y := int(math.Floor(y)) & 255
	Z := int(math.Floor(z)) & 255
	x -= math.Floor(x)
	y -= math.Floor(y)
	z -= math.Floor(z)

	u := fade(x)
	v := fade(y)
	w := fade(z)
	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))))
}