Simplex noise custom node for Shader Graph

SimplexNoise3Node.cs

//
// Simplex noise custom node for Shader Graph
//
// Original work (webgl-noise) Copyright (C) 2011 Ashima Arts.
// Translation and modification was made by Keijiro Takahashi.
// Ported to Shader Graph by Sergio L. Valladares
//
// This shader is based on the webgl-noise GLSL shader. For further details
// of the original shader, please see the following description from the
// original source code.
//
//
// Description : Array and textureless GLSL 2D/3D/4D simplex
//               noise functions.
//      Author : Ian McEwan, Ashima Arts.
//  Maintainer : ijm
//     Lastmod : 20110822 (ijm)
//     License : Copyright (C) 2011 Ashima Arts. All rights reserved.
//               Distributed under the MIT License. See LICENSE file.
//               https://github.com/ashima/webgl-noise
//

using UnityEngine;
using UnityEditor.ShaderGraph;
using System.Reflection;


[Title("Custom", "Simplex Noise 3D")]
public class SimplexNoise3Node : CodeFunctionNode
{

	public SimplexNoise3Node()
	{
		name = "Simplex Noise 3D";
	}


	public override bool hasPreview { get { return true; } }


	protected override MethodInfo GetFunctionToConvert()
	{
		return GetType().GetMethod("NoiseFunction", BindingFlags.Static | BindingFlags.NonPublic);
	}


	static string NoiseFunction(
		[Slot(0, Binding.WorldSpacePosition)] Vector3 Vertex,
		[Slot(1, Binding.None)] out Vector1 Noise,
		[Slot(2, Binding.None)] out Vector3 Gradient)
	{
		Gradient = Vector3.zero;
		return @"
			{
				float4 noise_vector = snoise_grad(Vertex);
				Noise = noise_vector.w;
				Gradient = noise_vector.xyz;
			} 
		";
	}


	public override void GenerateNodeFunction(FunctionRegistry registry, GraphContext graphContext, GenerationMode generationMode)
	{
		registry.ProvideFunction("mod289_3", s => s.Append(@"
			float3 mod289_3(float3 x)
			{
				return x - floor(x / 289.0) * 289.0;
			}
		"));

		registry.ProvideFunction("mod289_4", s => s.Append(@"
			float4 mod289_4(float4 x)
			{
				return x - floor(x / 289.0) * 289.0;
			}
		"));

		registry.ProvideFunction("permute", s => s.Append(@"
			float4 permute(float4 x)
			{
				return mod289_4((x * 34.0 + 1.0) * x);
			}
		"));

		registry.ProvideFunction("taylorInvSqrt", s => s.Append(@"
			float4 taylorInvSqrt(float4 r)
			{
				return 1.79284291400159 - r * 0.85373472095314;
			}
		"));

		registry.ProvideFunction("snoise_grad", s => s.Append(@"
			float4 snoise_grad(float3 v)
			{
				const float2 C = float2(1.0 / 6.0, 1.0 / 3.0);

				// First corner
				float3 i  = floor(v + dot(v, C.yyy));
				float3 x0 = v   - i + dot(i, C.xxx);

				// Other corners
				float3 g = step(x0.yzx, x0.xyz);
				float3 l = 1.0 - g;
				float3 i1 = min(g.xyz, l.zxy);
				float3 i2 = max(g.xyz, l.zxy);

				// x1 = x0 - i1  + 1.0 * C.xxx;
				// x2 = x0 - i2  + 2.0 * C.xxx;
				// x3 = x0 - 1.0 + 3.0 * C.xxx;
				float3 x1 = x0 - i1 + C.xxx;
				float3 x2 = x0 - i2 + C.yyy;
				float3 x3 = x0 - 0.5;

				// Permutations
				i = mod289_3(i); // Avoid truncation effects in permutation
				float4 p =
				  permute(permute(permute(i.z + float4(0.0, i1.z, i2.z, 1.0))
										+ i.y + float4(0.0, i1.y, i2.y, 1.0))
										+ i.x + float4(0.0, i1.x, i2.x, 1.0));

				// Gradients: 7x7 points over a square, mapped onto an octahedron.
				// The ring size 17*17 = 289 is close to a multiple of 49 (49*6 = 294)
				float4 j = p - 49.0 * floor(p / 49.0);  // mod(p,7*7)

				float4 x_ = floor(j / 7.0);
				float4 y_ = floor(j - 7.0 * x_);  // mod(j,N)

				float4 x = (x_ * 2.0 + 0.5) / 7.0 - 1.0;
				float4 y = (y_ * 2.0 + 0.5) / 7.0 - 1.0;

				float4 h = 1.0 - abs(x) - abs(y);

				float4 b0 = float4(x.xy, y.xy);
				float4 b1 = float4(x.zw, y.zw);

				//float4 s0 = float4(lessThan(b0, 0.0)) * 2.0 - 1.0;
				//float4 s1 = float4(lessThan(b1, 0.0)) * 2.0 - 1.0;
				float4 s0 = floor(b0) * 2.0 + 1.0;
				float4 s1 = floor(b1) * 2.0 + 1.0;
				float4 sh = -step(h, 0.0);

				float4 a0 = b0.xzyw + s0.xzyw * sh.xxyy;
				float4 a1 = b1.xzyw + s1.xzyw * sh.zzww;

				float3 g0 = float3(a0.xy, h.x);
				float3 g1 = float3(a0.zw, h.y);
				float3 g2 = float3(a1.xy, h.z);
				float3 g3 = float3(a1.zw, h.w);

				// Normalise gradients
				float4 norm = taylorInvSqrt(float4(dot(g0, g0), dot(g1, g1), dot(g2, g2), dot(g3, g3)));
				g0 *= norm.x;
				g1 *= norm.y;
				g2 *= norm.z;
				g3 *= norm.w;

				// Compute noise and gradient at P
				float4 m = max(0.6 - float4(dot(x0, x0), dot(x1, x1), dot(x2, x2), dot(x3, x3)), 0.0);
				float4 m2 = m * m;
				float4 m3 = m2 * m;
				float4 m4 = m2 * m2;
				float3 grad =
					-6.0 * m3.x * x0 * dot(x0, g0) + m4.x * g0 +
					-6.0 * m3.y * x1 * dot(x1, g1) + m4.y * g1 +
					-6.0 * m3.z * x2 * dot(x2, g2) + m4.z * g2 +
					-6.0 * m3.w * x3 * dot(x3, g3) + m4.w * g3;
				float4 px = float4(dot(x0, g0), dot(x1, g1), dot(x2, g2), dot(x3, g3));
				return 42.0 * float4(grad, dot(m4, px));
			}
			"));

		base.GenerateNodeFunction(registry, graphContext, generationMode);
	}

}

Hi! Thanks for this, it was helpful.

As Unity changed the API for the CodeFunctionNode in 2019.1 - https://forum.unity.com/threads/unable-to-create-custom-shader-graph-node-due-to-inaccessibility-of-customfunctionnode-class.586876/?_ga=2.254749640.1300780445.1603731888-1478299893.1603731888

So, I made an updated HLSL version of your gist:
https://gist.github.com/ma77os/de66fd807cbd77eac4d3a9023b590c7a

Best