// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only

#include "bsdf.glsllib"
#include "principledMaterialFresnel.glsllib"

vec4 qt_specularGGXBSDF(in vec3 normal, in vec3 L, in vec3 V, in vec3 lightSpecular, in vec3 F0, in vec3 F90, in float roughness)
{
    roughness = clamp(roughness, 0.00001, 1.0);
    float NdotL = dot(normal, L);
    float cNdotL = max(0.0, NdotL);
    float NdotV = dot(normal, V);
    float cNdotV = max(0.0, NdotV);
    vec3 H = normalize(V + L);
    float cLdotH = max(0.0, dot(L, H));
    float cNdotH = max(0.0, dot(normal, H));
    float alpha_ggx = roughness * roughness;
    float GGX_D = qt_D_GGX(cNdotH, alpha_ggx);
    float GGX_V = qt_V_GGX(cNdotL, cNdotV, alpha_ggx);

    float cLdotH5 = qt_schlick(cLdotH);
    vec3 F = mix(vec3(cLdotH5), F90, F0);

    vec3 specular_brdf_NL = cNdotL * GGX_D * F * GGX_V;

    return vec4(specular_brdf_NL * lightSpecular, 1.0);
}