ScriptableRenderPipeline/com.unity.shadergraph/Editor/Data/Nodes/Procedural/Noise/SimpleNoiseNode.cs

using System.Reflection;
using UnityEngine;

namespace UnityEditor.ShaderGraph
{
    [Title("Procedural", "Noise", "Simple Noise")]
    public class NoiseNode : CodeFunctionNode
    {
        public NoiseNode()
        {
            name = "Simple Noise";
        }

        public override string documentationURL
        {
            get { return "https://github.com/Unity-Technologies/ShaderGraph/wiki/Simple-Noise-Node"; }
        }

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

        static string Unity_SimpleNoise(
            [Slot(0, Binding.MeshUV0)] Vector2 UV,
            [Slot(1, Binding.None, 500f, 500f, 500f, 500f)] Vector1 Scale,
            [Slot(2, Binding.None)] out Vector1 Out)
        {
            return
                @"
{
    float t = 0.0;

    float freq = pow(2.0, float(0));
    float amp = pow(0.5, float(3-0));
    t += unity_valueNoise(float2(UV.x*Scale/freq, UV.y*Scale/freq))*amp;

    freq = pow(2.0, float(1));
    amp = pow(0.5, float(3-1));
    t += unity_valueNoise(float2(UV.x*Scale/freq, UV.y*Scale/freq))*amp;

    freq = pow(2.0, float(2));
    amp = pow(0.5, float(3-2));
    t += unity_valueNoise(float2(UV.x*Scale/freq, UV.y*Scale/freq))*amp;

    Out = t;
}
";
        }

        public override void GenerateNodeFunction(FunctionRegistry registry, GraphContext graphContext, GenerationMode generationMode)
        {
            registry.ProvideFunction("unity_noise_randomValue", s => s.Append(@"
inline float unity_noise_randomValue (float2 uv)
{
    return frac(sin(dot(uv, float2(12.9898, 78.233)))*43758.5453);
}"));

            registry.ProvideFunction("unity_noise_interpolate", s => s.Append(@"
inline float unity_noise_interpolate (float a, float b, float t)
{
    return (1.0-t)*a + (t*b);
}
"));

            registry.ProvideFunction("unity_valueNoise", s => s.Append(@"
inline float unity_valueNoise (float2 uv)
{
    float2 i = floor(uv);
    float2 f = frac(uv);
    f = f * f * (3.0 - 2.0 * f);

    uv = abs(frac(uv) - 0.5);
    float2 c0 = i + float2(0.0, 0.0);
    float2 c1 = i + float2(1.0, 0.0);
    float2 c2 = i + float2(0.0, 1.0);
    float2 c3 = i + float2(1.0, 1.0);
    float r0 = unity_noise_randomValue(c0);
    float r1 = unity_noise_randomValue(c1);
    float r2 = unity_noise_randomValue(c2);
    float r3 = unity_noise_randomValue(c3);

    float bottomOfGrid = unity_noise_interpolate(r0, r1, f.x);
    float topOfGrid = unity_noise_interpolate(r2, r3, f.x);
    float t = unity_noise_interpolate(bottomOfGrid, topOfGrid, f.y);
    return t;
}"));

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