89 lines
2.9 KiB
Go
89 lines
2.9 KiB
Go
package main
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import (
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"fmt"
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"math"
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)
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func main() {
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fmt.Println(noise(3.14, 42, 7))
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}
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func noise(x, y, z float64) float64 {
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X := int(math.Floor(x)) & 255
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Y := int(math.Floor(y)) & 255
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Z := int(math.Floor(z)) & 255
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x -= math.Floor(x)
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y -= math.Floor(y)
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z -= math.Floor(z)
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u := fade(x)
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v := fade(y)
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w := fade(z)
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A := p[X] + Y
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AA := p[A] + Z
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AB := p[A+1] + Z
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B := p[X+1] + Y
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BA := p[B] + Z
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BB := p[B+1] + Z
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return lerp(w, lerp(v, lerp(u, grad(p[AA], x, y, z),
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grad(p[BA], x-1, y, z)),
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lerp(u, grad(p[AB], x, y-1, z),
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grad(p[BB], x-1, y-1, z))),
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lerp(v, lerp(u, grad(p[AA+1], x, y, z-1),
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grad(p[BA+1], x-1, y, z-1)),
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lerp(u, grad(p[AB+1], x, y-1, z-1),
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grad(p[BB+1], x-1, y-1, z-1))))
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}
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func fade(t float64) float64 { return t * t * t * (t*(t*6-15) + 10) }
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func lerp(t, a, b float64) float64 { return a + t*(b-a) }
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func grad(hash int, x, y, z float64) float64 {
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// Go doesn't have a ternary. Ternaries can be translated directly
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// with if statements, but chains of if statements are often better
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// expressed with switch statements.
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switch hash & 15 {
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case 0, 12:
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return x + y
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case 1, 14:
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return y - x
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case 2:
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return x - y
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case 3:
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return -x - y
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case 4:
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return x + z
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case 5:
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return z - x
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case 6:
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return x - z
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case 7:
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return -x - z
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case 8:
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return y + z
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case 9, 13:
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return z - y
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case 10:
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return y - z
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}
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// case 11, 16:
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return -y - z
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}
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var permutation = []int{
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151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225,
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140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148,
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247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32,
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57, 177, 33, 88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175,
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74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122,
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60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102, 143, 54,
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65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169,
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200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64,
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52, 217, 226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212,
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207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42, 223, 183, 170, 213,
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119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
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129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104,
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218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241,
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81, 51, 145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157,
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184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93,
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222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180,
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}
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var p = append(permutation, permutation...)
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