109 lines
4.0 KiB
C#
109 lines
4.0 KiB
C#
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//
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// Description : Array and textureless GLSL 2D/3D/4D simplex
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// noise functions.
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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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/// <param name="gradient">Output 3D noise gradient.</param>
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/// <returns>Noise value.</returns>
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public static float snoise(float3 v, out float3 gradient)
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{
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float2 C = float2(1.0f / 6.0f, 1.0f / 3.0f);
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float4 D = float4(0.0f, 0.5f, 1.0f, 2.0f);
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// First corner
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float3 i = floor(v + dot(v, C.yyy));
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float3 x0 = v - i + dot(i, C.xxx);
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// Other corners
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float3 g = step(x0.yzx, x0.xyz);
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float3 l = 1.0f - g;
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float3 i1 = min(g.xyz, l.zxy);
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float3 i2 = max(g.xyz, l.zxy);
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// x0 = x0 - 0.0 + 0.0 * C.xxx;
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// x1 = x0 - i1 + 1.0 * C.xxx;
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// x2 = x0 - i2 + 2.0 * C.xxx;
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// x3 = x0 - 1.0 + 3.0 * C.xxx;
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float3 x1 = x0 - i1 + C.xxx;
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float3 x2 = x0 - i2 + C.yyy; // 2.0*C.x = 1/3 = C.y
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float3 x3 = x0 - D.yyy; // -1.0+3.0*C.x = -0.5 = -D.y
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// Permutations
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i = mod289(i);
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float4 p = permute(permute(permute(
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i.z + float4(0.0f, i1.z, i2.z, 1.0f))
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+ i.y + float4(0.0f, i1.y, i2.y, 1.0f))
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+ i.x + float4(0.0f, i1.x, i2.x, 1.0f));
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// Gradients: 7x7 points over a square, mapped onto an octahedron.
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// The ring size 17*17 = 289 is close to a multiple of 49 (49*6 = 294)
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float n_ = 0.142857142857f; // 1.0/7.0
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float3 ns = n_ * D.wyz - D.xzx;
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float4 j = p - 49.0f * floor(p * ns.z * ns.z); // math.mod(p,7*7)
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float4 x_ = floor(j * ns.z);
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float4 y_ = floor(j - 7.0f * x_); // math.mod(j,N)
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float4 x = x_ * ns.x + ns.yyyy;
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float4 y = y_ * ns.x + ns.yyyy;
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float4 h = 1.0f - abs(x) - abs(y);
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float4 b0 = float4(x.xy, y.xy);
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float4 b1 = float4(x.zw, y.zw);
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//float4 s0 = float4(math.lessThan(b0,0.0))*2.0 - 1.0;
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//float4 s1 = float4(math.lessThan(b1,0.0))*2.0 - 1.0;
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float4 s0 = floor(b0) * 2.0f + 1.0f;
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float4 s1 = floor(b1) * 2.0f + 1.0f;
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float4 sh = -step(h, float4(0.0f));
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float4 a0 = b0.xzyw + s0.xzyw * sh.xxyy;
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float4 a1 = b1.xzyw + s1.xzyw * sh.zzww;
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float3 p0 = float3(a0.xy, h.x);
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float3 p1 = float3(a0.zw, h.y);
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float3 p2 = float3(a1.xy, h.z);
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float3 p3 = float3(a1.zw, h.w);
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//Normalise gradients
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float4 norm = taylorInvSqrt(float4(dot(p0, p0), dot(p1, p1), dot(p2, p2), dot(p3, p3)));
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p0 *= norm.x;
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p1 *= norm.y;
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p2 *= norm.z;
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p3 *= norm.w;
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// Mix final noise value
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float4 m = max(0.6f - float4(dot(x0, x0), dot(x1, x1), dot(x2, x2), dot(x3, x3)), 0.0f);
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float4 m2 = m * m;
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float4 m4 = m2 * m2;
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float4 pdotx = float4(dot(p0, x0), dot(p1, x1), dot(p2, x2), dot(p3, x3));
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// Determath.mine noise gradient
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float4 temp = m2 * m * pdotx;
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gradient = -8.0f * (temp.x * x0 + temp.y * x1 + temp.z * x2 + temp.w * x3);
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gradient += m4.x * p0 + m4.y * p1 + m4.z * p2 + m4.w * p3;
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gradient *= 42.0f;
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return 42.0f * dot(m4, pdotx);
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}
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}
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}
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