Ipseity-Demo/Assets/_Content/Shaders/EnkiBillal/Include/EnkiBiIlal.hlsl

#ifndef ENKI_BILLAL_INCLUDED
#define ENKI_BILLAL_INCLUDED

#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
#include "Assets/_Content/Shaders/Include/Noises.hlsl"
#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/AmbientOcclusion.hlsl"

float2 RotateUV(float2 UV, float2 Pivot, float Angle)
{
    float s = sin(Angle);
    float c = cos(Angle);

    UV -= Pivot;

    float2 rotated = float2(
        UV.x * c - UV.y * s,
        UV.x * s + UV.y * c
    );

    return rotated + Pivot;
}

float3 GetScale(float3 PivotWS)
{
    return float3
    (
        length(TransformObjectToWorld(float3(1, 0, 0)) - PivotWS),
        length(TransformObjectToWorld(float3(0, 1, 0)) - PivotWS),
        length(TransformObjectToWorld(float3(0, 0, 1)) - PivotWS)
    );
}

float GetShadow(float3 PositionWS)
{
    float4 shadowCoord = TransformWorldToShadowCoord(PositionWS);
    Light mainLight = GetMainLight(shadowCoord);

    float shadow = 1 - mainLight.shadowAttenuation;

#if defined(_ADDITIONAL_LIGHTS)
    uint lightsCount = GetAdditionalLightsCount();

    [loop]
    for (uint i = 0; i < lightsCount; i++)
    {
        Light light = GetAdditionalLight(i, PositionWS);
        shadow = max(shadow, 1 - light.shadowAttenuation);
    }
#endif

    return saturate(shadow);
}

void GetDetailLOD
(
    float Depth,
    float DetailSize,
    float LODJitter,
    out float DetailSizeA,
    out float DetailSizeB,
    out float LODBlend
)
{
    const float lodRatio = 4;
    const float lodSize = DetailSize / lodRatio * 2;

    float dist = max(Depth, 1e-5);
    float lod = log(dist) / log(lodRatio) + LODJitter; // log2(dist);

    float lodFloor = floor(lod);
    float lodFrac = lod - lodFloor;

    LODBlend = lodFrac * lodFrac * (3 - 2 * lodFrac);

    DetailSizeA = lodSize * pow(lodRatio, lodFloor);
    DetailSizeB = lodSize * pow(lodRatio, lodFloor + 1);
}

float4 SampleBombedTexture
(
    UnityTexture2D Tex,
    float2 UV
)
{
    const float cellBlend = 4;
    
    float2 cell = floor(UV);
    float2 local = frac(UV);

    float4 result = 0;
    float weightSum = 0;

    [unroll]
    for (int y = 0; y < 2; y++)
    {
        [unroll]
        for (int x = 0; x < 2; x++)
        {
            float2 currentCell = cell + float2(x, y);

            float2 randomOffset = (Hash2D(currentCell) - .5) * .35;
            float randomAngle = Hash1From2D(currentCell) * TWO_PI;

            float2 center = float2(x, y) + randomOffset;
            float2 delta = local - center;

            float weight =
                pow(saturate(1 - abs(delta.x)), cellBlend) *
                pow(saturate(1 - abs(delta.y)), cellBlend);

            float2 sampleUV = UV + randomOffset;

            sampleUV = RotateUV
            (
                sampleUV,
                currentCell + .5,
                randomAngle
            );

            result += Tex.tex.Sample
            (
                Tex.samplerstate,
                sampleUV
            ) * weight;

            weightSum += weight;
        }
    }

    return result / max(weightSum, 1e-5);
}

struct ProjectionData
{
    float2 uv[7];
    float mask[7];
};

ProjectionData GetProjections
(
    float3 PositionOS,
    float3 NormalOS,
    float ProjectionBlend
)
{
    ProjectionData data;

    float3 normal = normalize(NormalOS);

    float3 projectionNormals[7] =
    {
        normalize(float3(1, 1, 1)),
        normalize(float3(-1, 1, 1)),
        normalize(float3(1, -1, 1)),
        normalize(float3(-1, -1, 1)),
        float3(1, 0, 0),
        float3(0, 1, 0),
        float3(0, 0, 1)
    };

    float sharpness = lerp(2, 32, saturate(ProjectionBlend));

    float maskSum = 0;

    [unroll]
    for (int i = 0; i < 7; i++)
    {
        float3 n = projectionNormals[i];

        float d = abs(dot(normal, n));

        data.mask[i] = pow(saturate(d), sharpness);
        maskSum += data.mask[i];

        float3 up = abs(n.y) < .999
            ? float3(0, 1, 0)
            : float3(1, 0, 0);

        float3 tangent = normalize(cross(up, n));
        float3 bitangent = normalize(cross(n, tangent));

        data.uv[i] = float2
        (
            dot(PositionOS, tangent),
            dot(PositionOS, bitangent)
        );
    }

    maskSum = max(maskSum, 1e-5);

    [unroll]
    for (int i = 0; i < 7; i++)
        data.mask[i] /= maskSum;

    return data;
}

float4 SampleProjectedDetailLOD
(
    UnityTexture2D DetailTex,
    float3 PositionOS,
    float3 NormalOS,
    float ProjectionBlend,
    float DetailSize,
    float Depth
)
{
    const float lodJitterStrength = .8;
    const float lodJitterSize = 1.5;

    float4 detail = 0;
    float totalMask = 0;

    ProjectionData projections = GetProjections
    (
        PositionOS,
        NormalOS,
        ProjectionBlend
    );

    [unroll]
    for (int i = 0; i < 7; i++)
    {
        float mask = projections.mask[i];

        float lodJitter = (Hash1From2D(floor(projections.uv[i] * lodJitterSize) + i * 17.13) - .5) * lodJitterStrength;

        float detailSizeA;
        float detailSizeB;
        float lodBlend;

        GetDetailLOD
        (
            Depth,
            DetailSize,
            lodJitter,
            detailSizeA,
            detailSizeB,
            lodBlend
        );

        float4 detailA = SampleBombedTexture
        (
            DetailTex,
            projections.uv[i] / detailSizeA
        );

        float4 detailB = SampleBombedTexture
        (
            DetailTex,
            projections.uv[i] / detailSizeB
        );

        detail += lerp(detailA, detailB, lodBlend) * mask;
        totalMask += mask;
    }

    return detail / max(totalMask, 1e-5);
}

void EnkiBillal_float
(
    float4 Color,
    UnityTexture2D DetailTex,
    float2 ScreenUV,
    float3 PositionWS,
    float3 NormalWS,
    float ProjectionsBlend,
    float DetailSize,
    float4 FogColor,
    float FogMin,
    float FogMax,
    out float3 Output
)
{
    // Common
    float depth = length(PositionWS - _WorldSpaceCameraPos.xyz);
    
    float3 pivotWS = TransformObjectToWorld(float3(0, 0, 0));

    float3 scale = GetScale(pivotWS);
    
    float3 positionOS = TransformWorldToObject(PositionWS) * scale;
    float3 normalOS = normalize(TransformWorldToObjectDir(NormalWS));
    
    //float ao = GetScreenSpaceAmbientOcclusion(ScreenUV).directAmbientOcclusion;
    
    // Shadow

    float shadow = GetShadow(PositionWS);
    float shadowAtten = Remap(1, 0, .6, 1, shadow);

    // Detail
    
    float4 detail = SampleProjectedDetailLOD
    (
        DetailTex,
        positionOS,
        normalOS,
        ProjectionsBlend,
        DetailSize,
        depth
    
    );
    
    float detailMask = smoothstep(0, .8, detail.a);
    
    // Fog
    
    // Output
    
    Output = Color.rgb;
    Output = lerp(Output.rgb, detail.rgb, detailMask);
    Output = lerp(Output.rgb, FogColor.rgb, smoothstep(FogMin, FogMax, depth) * FogColor.a);
}

#endif