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1226
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1 proc randomGradient(pos: Vec2f, seed: int32 = 0): Vec2f =
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2 let randomAngle: float32 = TAU * (float32(int(hash((pos.x, pos.y, seed)))) / float32(high(int)))
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3 return NewVec2f(cos(randomAngle), sin(randomAngle))
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4
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5 proc interpolate(a: float32, b: float32, weight: float32): float32 =
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6 # with Smootherstep
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7 (b - a) * ((weight * (weight * 6.0 - 15.0) + 10.0) * weight * weight * weight) + a;
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8
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9 proc Perlin*(pos: Vec2f, seed: int32 = 0): float32 =
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10 let
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11 # grid coordinates around target point
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12 topleft = NewVec2f(trunc(pos.x), trunc(pos.y))
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13 topright = topleft + NewVec2f(1, 0)
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14 bottomleft = topleft + NewVec2f(0, 1)
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15 bottomright = topleft + NewVec2f(1, 1)
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16 # products for weights
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17 topleft_dot = topleft.randomGradient(seed).Dot((pos - topleft))
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18 topright_dot = topright.randomGradient(seed).Dot((pos - topright))
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19 bottomleft_dot = bottomleft.randomGradient(seed).Dot((pos - bottomleft))
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20 bottomright_dot = bottomright.randomGradient(seed).Dot((pos - bottomright))
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21 xinterpol = pos.x - topleft.x
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22 yinterpol = pos.y - topleft.y
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23
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24 return interpolate(
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25 interpolate(topleft_dot, bottomleft_dot, yinterpol),
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26 interpolate(topright_dot, bottomright_dot, yinterpol),
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27 xinterpol
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28 )
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