ScriptableRenderPipeline/Assets/ScriptableRenderLoop/HDRenderLoop/Lighting/SinglePass/SinglePassLoop.hlsl

//-----------------------------------------------------------------------------
// LightLoop
// ----------------------------------------------------------------------------

// bakeDiffuseLighting is part of the prototype so a user is able to implement a "base pass" with GI and multipass direct light (aka old unity rendering path)
void LightLoop(	float3 V, float3 positionWS, Coordinate coord, PreLightData prelightData, BSDFData bsdfData, float3 bakeDiffuseLighting,
                out float3 diffuseLighting,
                out float3 specularLighting)
{
    LightLoopContext context;
    ZERO_INITIALIZE(LightLoopContext, context);

    diffuseLighting  = float3(0.0, 0.0, 0.0);
    specularLighting = float3(0.0, 0.0, 0.0);

    uint i = 0; // Declare once to avoid the D3D11 compiler warning.

    for (i = 0; i < _DirectionalLightCount; ++i)
    {
        float3 localDiffuseLighting, localSpecularLighting;

        EvaluateBSDF_Directional(   context, V, positionWS, prelightData, _DirectionalLightList[i], bsdfData,
                                    localDiffuseLighting, localSpecularLighting);

        diffuseLighting += localDiffuseLighting;
        specularLighting += localSpecularLighting;
    }

    for (i = 0; i < _PunctualLightCount; ++i)
    {
        float3 localDiffuseLighting, localSpecularLighting;

        EvaluateBSDF_Punctual(context, V, positionWS, prelightData, _PunctualLightList[i], bsdfData,
                              localDiffuseLighting, localSpecularLighting);

        diffuseLighting  += localDiffuseLighting;
        specularLighting += localSpecularLighting;
    }

    for (i = 0; i < _AreaLightCount; ++i)
    {
        float3 localDiffuseLighting, localSpecularLighting;

        if (_AreaLightList[i].lightType == GPULIGHTTYPE_LINE)
        {
            EvaluateBSDF_Line(context, V, positionWS, prelightData, _AreaLightList[i], bsdfData,
                              localDiffuseLighting, localSpecularLighting);
        }
        else
        {
            EvaluateBSDF_Area(context, V, positionWS, prelightData, _AreaLightList[i], bsdfData,
                              localDiffuseLighting, localSpecularLighting);
        }

        diffuseLighting  += localDiffuseLighting;
        specularLighting += localSpecularLighting;
    }

    // TODO: Check the reflection hierarchy, for the current system (matching legacy unity) we must sort from bigger solid angle to lower (lower override bigger). So begging by sky
    // TODO: Change the way it is done by reversing the order, from smaller solid angle to bigger, so we can early out when the weight is 1.
    float3 iblDiffuseLighting  = float3(0.0, 0.0, 0.0);
    float3 iblSpecularLighting = float3(0.0, 0.0, 0.0);

    // Only apply sky IBL if the sky texture is available.
    if (_EnvLightSkyEnabled)
    {
        float3 localDiffuseLighting, localSpecularLighting;
        float2 weight;
        // The sky is a single cubemap texture separate from the reflection probe texture array (different resolution and compression)
        context.sampleReflection = SINGLE_PASS_CONTEXT_SAMPLE_SKY;
        EnvLightData envLightSky = InitSkyEnvLightData(0); // The sky data are generated on the fly so the compiler can optimize the code
        EvaluateBSDF_Env(context, V, positionWS, prelightData, envLightSky, bsdfData, localDiffuseLighting, localSpecularLighting, weight);
        iblDiffuseLighting = lerp(iblDiffuseLighting, localDiffuseLighting, weight.x); // Should be remove by the compiler if it is smart as all is constant 0
        iblSpecularLighting = lerp(iblSpecularLighting, localSpecularLighting, weight.y);
    }

    for (i = 0; i < _EnvLightCount; ++i)
    {
        float3 localDiffuseLighting, localSpecularLighting;
        float2 weight;
        context.sampleReflection = SINGLE_PASS_CONTEXT_SAMPLE_REFLECTION_PROBES;
        EvaluateBSDF_Env(context, V, positionWS, prelightData, _EnvLightList[i], bsdfData, localDiffuseLighting, localSpecularLighting, weight);
        iblDiffuseLighting  = lerp(iblDiffuseLighting,  localDiffuseLighting,  weight.x); // Should be remove by the compiler if it is smart as all is constant 0
        iblSpecularLighting = lerp(iblSpecularLighting, localSpecularLighting, weight.y);
    }

    diffuseLighting  += iblDiffuseLighting;
    specularLighting += iblSpecularLighting;

    // Add indirect diffuse + emissive (if any)
    diffuseLighting += bakeDiffuseLighting;
}