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

#include "principledMaterialFresnel.glsllib"

// See https://disney-animation.s3.amazonaws.com/library/s2012_pbs_disney_brdf_notes_v2.pdf
vec4 qt_diffuseBurleyBSDF(in vec3 normal, in vec3 lightDirection, in vec3 viewVector, in vec3 lightDiffuse, in float roughness)
{
    vec3 H = normalize(viewVector + lightDirection);
    float cLdotH = max(0.0, dot(lightDirection, H));
    float cNdotV = max(0.0, dot(normal, viewVector));
    float cNdotL = max(0.0, dot(normal, lightDirection));

    float fLight = qt_schlick(cNdotL);
    float fView = qt_schlick(cNdotV);
    float fDiffuse90 = 0.5 + 2.0 * cLdotH * cLdotH * roughness;
    float fDiffuse = mix(1.0, fDiffuse90, fLight) * mix(1.0, fDiffuse90, fView);

    float factor = fDiffuse * cNdotL;

    return vec4(factor * lightDiffuse, 1.0);
}