/Operators/Lib/Assets/shaders/img/generate/Grain.hlsl

#include "shared/hash-functions.hlsl"

cbuffer ParamConstants : register(b0)
{
    float Amount;
    float Color;
    float Exponent;
    float Brightness;
    float Time;
    float Scale;
    float CleanMode;
}

cbuffer Resolution : register(b1)
{
    float TargetWidth;
    float TargetHeight;
}

struct vsOutput
{
    float4 position : SV_POSITION;
    float2 texCoord : TEXCOORD;
};

Texture2D<float4> ImageA : register(t0);
sampler texSampler : register(s0);

#define mod(x, y) (x - y * floor(x / y))
float IsBetween(float value, float low, float high)
{
    return (value >= low && value <= high) ? 1 : 0;
}

float4 GetNoiseFromRandom(float2 uv)
{
    // Animation
    float pxHash = hash12(uv * 431 + 111);
    float t = Time + pxHash;

    // Color Noise
    float4 hash1 = hash42((uv * 431 + (int)t));
    float4 hash2 = hash42((uv * 431 + (int)t + 1));
    float4 hash = lerp(hash1, hash2, t % 1);

    float4 grayScale = (hash.r + hash.g + hash.b) / 3;
    float4 noise = (lerp(grayScale, hash, Color) - 0.5) * 2;

    noise = noise < 0
                ? -pow(-noise, Exponent)
                : pow(noise, Exponent);

    noise += Brightness;
    return noise;
}

float4 psMain(vsOutput psInput) : SV_TARGET
{
    float2 uv = psInput.texCoord;
    float4 orgColor = ImageA.Sample(texSampler, uv);

    if (Scale > 1)
    {
        float2 pixelStep = float2(1.0 / TargetWidth, 1.0 / TargetHeight);
        float2 offset = Scale * pixelStep;
        float2 fraction = uv % offset;

        if (CleanMode > 0.5)
        {
            // CLEAN VERSION - no stripes
            float2 cellIndex = floor(uv / offset);
            float4 noise = GetNoiseFromRandom(cellIndex);
            float4 color = float4(orgColor.rgb + noise.rgb * Amount, 1);
            return color;
        }
        else
        {
            // ORIGINAL VERSION - maintains the unique stripe style
            float4 n1 = GetNoiseFromRandom(uv - fraction + 0.001 * pixelStep);
            float4 n2 = GetNoiseFromRandom(uv - fraction + 0.004 * pixelStep + offset);
            float4 noise = lerp(n1, n2, 0);
            float4 color = float4(orgColor.rgb + noise.rgb * Amount, 1);
            return color;
        }
    }
    else
    {
        float4 noise = GetNoiseFromRandom(uv);
        float4 color = float4(orgColor.rgb + noise.rgb * Amount, 1);
        return color;
    }
}