74 lines
2.7 KiB
C#
74 lines
2.7 KiB
C#
//
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// Description : Array and textureless GLSL 2D simplex noise function.
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// Author : Ian McEwan, Ashima Arts.
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// Maintainer : stegu
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// Lastmath.mod : 20110822 (ijm)
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// License : Copyright (C) 2011 Ashima Arts. All rights reserved.
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// Distributed under the MIT License. See LICENSE file.
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// https://github.com/ashima/webgl-noise
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// https://github.com/stegu/webgl-noise
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//
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using static Unity.Mathematics.math;
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namespace Unity.Mathematics
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{
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public static partial class noise
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{
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/// <summary>
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/// Simplex noise.
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/// </summary>
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/// <param name="v">Input coordinate.</param>
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/// <returns>Noise value.</returns>
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public static float snoise(float2 v)
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{
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float4 C = float4(0.211324865405187f, // (3.0-math.sqrt(3.0))/6.0
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0.366025403784439f, // 0.5*(math.sqrt(3.0)-1.0)
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-0.577350269189626f, // -1.0 + 2.0 * C.x
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0.024390243902439f); // 1.0 / 41.0
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// First corner
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float2 i = floor(v + dot(v, C.yy));
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float2 x0 = v - i + dot(i, C.xx);
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// Other corners
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float2 i1;
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//i1.x = math.step( x0.y, x0.x ); // x0.x > x0.y ? 1.0 : 0.0
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//i1.y = 1.0 - i1.x;
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i1 = (x0.x > x0.y) ? float2(1.0f, 0.0f) : float2(0.0f, 1.0f);
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// x0 = x0 - 0.0 + 0.0 * C.xx ;
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// x1 = x0 - i1 + 1.0 * C.xx ;
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// x2 = x0 - 1.0 + 2.0 * C.xx ;
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float4 x12 = x0.xyxy + C.xxzz;
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x12.xy -= i1;
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// Permutations
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i = mod289(i); // Avoid truncation effects in permutation
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float3 p = permute(permute(i.y + float3(0.0f, i1.y, 1.0f)) + i.x + float3(0.0f, i1.x, 1.0f));
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float3 m = max(0.5f - float3(dot(x0, x0), dot(x12.xy, x12.xy), dot(x12.zw, x12.zw)), 0.0f);
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m = m * m;
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m = m * m;
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// Gradients: 41 points uniformly over a line, mapped onto a diamond.
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// The ring size 17*17 = 289 is close to a multiple of 41 (41*7 = 287)
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float3 x = 2.0f * frac(p * C.www) - 1.0f;
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float3 h = abs(x) - 0.5f;
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float3 ox = floor(x + 0.5f);
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float3 a0 = x - ox;
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// Normalise gradients implicitly by scaling m
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// Approximation of: m *= inversemath.sqrt( a0*a0 + h*h );
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m *= 1.79284291400159f - 0.85373472095314f * (a0 * a0 + h * h);
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// Compute final noise value at P
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float gx = a0.x * x0.x + h.x * x0.y;
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float2 gyz = a0.yz * x12.xz + h.yz * x12.yw;
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float3 g = float3(gx,gyz);
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return 130.0f * dot(m, g);
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}
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}
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}
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