#ifndef BADDOG_PREINTEGRATED_FGD_INCLUDED
#define BADDOG_PREINTEGRATED_FGD_INCLUDED

#include "Packages/com.baddog.rendering.arealight/Shaders/PreIntegratedFGD.cs.hlsl"
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/GlobalSamplers.hlsl"

//-----------------------------------------------------------------------------
// Pre-Integrated FGD Texture Declarations
//-----------------------------------------------------------------------------

// Pre-integrated FGD (Fresnel, Geometric, Diffuse) textures
// These textures store pre-computed BSDF integrals for efficient IBL and area light evaluation
TEXTURE2D(_PreIntegratedFGD_GGXDisneyDiffuse);
TEXTURE2D(_PreIntegratedFGD_CharlieAndFabric);
TEXTURE2D(_PreIntegratedFGD_Marschner);

// Use URP's standard linear clamp sampler from GlobalSamplers.hlsl
// sampler_LinearClamp is defined in GlobalSamplers.hlsl and can be used directly

//-----------------------------------------------------------------------------
// Pre-Integrated FGD Functions (GGX + Disney Diffuse)
//-----------------------------------------------------------------------------

// For image based lighting, a part of the BSDF is pre-integrated.
// This is done both for specular GGX height-correlated and DisneyDiffuse
// reflectivity is Integral{(BSDF_GGX / F)} - use for multiscattering
void GetPreIntegratedFGDGGXAndDisneyDiffuse(float NdotV, float perceptualRoughness, float3 fresnel0, float F90, out float3 specularFGD, out float diffuseFGD, out float reflectivity)
{
    // We want the LUT to contain the entire [0, 1] range, without losing half a texel at each side.
    float2 coordLUT = Remap01ToHalfTexelCoord(float2(sqrt(NdotV), perceptualRoughness), FGDTEXTURE_RESOLUTION);

    float3 preFGD = SAMPLE_TEXTURE2D_LOD(_PreIntegratedFGD_GGXDisneyDiffuse, sampler_LinearClamp, coordLUT, 0).xyz;

    // Pre-integrate GGX FGD
    // Integral{BSDF * <N,L> dw} =
    // Integral{(F0 + (F90 - F0) * (1 - <V,H>)^5) * (BSDF / F) * <N,L> dw} =
    // (F90 - F0) * Integral{(1 - <V,H>)^5 * (BSDF / F) * <N,L> dw} + F0 * Integral{(BSDF / F) * <N,L> dw}=
    // (F90 - F0) * x + F0 * y
    specularFGD = (F90 - fresnel0) * preFGD.xxx + fresnel0 * preFGD.yyy;

    // Pre integrate DisneyDiffuse FGD:
    // z = DisneyDiffuse
    // Remap from the [0, 1] to the [0.5, 1.5] range.
    diffuseFGD = preFGD.z + 0.5;

    reflectivity = preFGD.y;
}

// Overload without F90 parameter (defaults to 1.0)
void GetPreIntegratedFGDGGXAndDisneyDiffuse(float NdotV, float perceptualRoughness, float3 fresnel0, out float3 specularFGD, out float diffuseFGD, out float reflectivity)
{
    GetPreIntegratedFGDGGXAndDisneyDiffuse(NdotV, perceptualRoughness, fresnel0, 1.0, specularFGD, diffuseFGD, reflectivity);
}

// GGX + Lambert variant (for USE_DIFFUSE_LAMBERT_BRDF)
void GetPreIntegratedFGDGGXAndLambert(float NdotV, float perceptualRoughness, float3 fresnel0, out float3 specularFGD, out float diffuseFGD, out float reflectivity)
{
    GetPreIntegratedFGDGGXAndDisneyDiffuse(NdotV, perceptualRoughness, fresnel0, specularFGD, diffuseFGD, reflectivity);
    diffuseFGD = 1.0;
}

//-----------------------------------------------------------------------------
// Pre-Integrated FGD Functions (Charlie + Fabric Lambert)
//-----------------------------------------------------------------------------

void GetPreIntegratedFGDCharlieAndFabricLambert(float NdotV, float perceptualRoughness, float3 fresnel0, out float3 specularFGD, out float diffuseFGD, out float reflectivity)
{
    // Read the texture
    float3 preFGD = SAMPLE_TEXTURE2D_LOD(_PreIntegratedFGD_CharlieAndFabric, sampler_LinearClamp, float2(NdotV, perceptualRoughness), 0).xyz;

    specularFGD = lerp(preFGD.xxx, preFGD.yyy, fresnel0) * 2.0 * PI;

    // z = FabricLambert
    diffuseFGD = preFGD.z;

    reflectivity = preFGD.y;
}

#endif // BADDOG_PREINTEGRATED_FGD_INCLUDED