three
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JavaScript 3D library
215 lines (134 loc) • 7.74 kB
JavaScript
export default /* glsl */`
struct PhysicalMaterial {
vec3 diffuseColor;
float roughness;
vec3 specularColor;
float specularF90;
float clearcoat;
float clearcoatRoughness;
vec3 clearcoatF0;
float clearcoatF90;
vec3 sheenColor;
float sheenRoughness;
};
// temporary
vec3 clearcoatSpecular = vec3( 0.0 );
vec3 sheenSpecular = vec3( 0.0 );
// This is a curve-fit approxmation to the "Charlie sheen" BRDF integrated over the hemisphere from
// Estevez and Kulla 2017, "Production Friendly Microfacet Sheen BRDF". The analysis can be found
// in the Sheen section of https://drive.google.com/file/d/1T0D1VSyR4AllqIJTQAraEIzjlb5h4FKH/view?usp=sharing
float IBLSheenBRDF( const in vec3 normal, const in vec3 viewDir, const in float roughness) {
float dotNV = saturate( dot( normal, viewDir ) );
float r2 = roughness * roughness;
float a = roughness < 0.25 ? -339.2 * r2 + 161.4 * roughness - 25.9 : -8.48 * r2 + 14.3 * roughness - 9.95;
float b = roughness < 0.25 ? 44.0 * r2 - 23.7 * roughness + 3.26 : 1.97 * r2 - 3.27 * roughness + 0.72;
float DG = exp( a * dotNV + b ) + ( roughness < 0.25 ? 0.0 : 0.1 * ( roughness - 0.25 ) );
return saturate( DG * RECIPROCAL_PI );
}
// Analytical approximation of the DFG LUT, one half of the
// split-sum approximation used in indirect specular lighting.
// via 'environmentBRDF' from "Physically Based Shading on Mobile"
// https://www.unrealengine.com/blog/physically-based-shading-on-mobile
vec2 DFGApprox( const in vec3 normal, const in vec3 viewDir, const in float roughness ) {
float dotNV = saturate( dot( normal, viewDir ) );
const vec4 c0 = vec4( - 1, - 0.0275, - 0.572, 0.022 );
const vec4 c1 = vec4( 1, 0.0425, 1.04, - 0.04 );
vec4 r = roughness * c0 + c1;
float a004 = min( r.x * r.x, exp2( - 9.28 * dotNV ) ) * r.x + r.y;
vec2 fab = vec2( - 1.04, 1.04 ) * a004 + r.zw;
return fab;
}
vec3 EnvironmentBRDF( const in vec3 normal, const in vec3 viewDir, const in vec3 specularColor, const in float specularF90, const in float roughness ) {
vec2 fab = DFGApprox( normal, viewDir, roughness );
return specularColor * fab.x + specularF90 * fab.y;
}
// Fdez-Agüera's "Multiple-Scattering Microfacet Model for Real-Time Image Based Lighting"
// Approximates multiscattering in order to preserve energy.
// http://www.jcgt.org/published/0008/01/03/
void computeMultiscattering( const in vec3 normal, const in vec3 viewDir, const in vec3 specularColor, const in float specularF90, const in float roughness, inout vec3 singleScatter, inout vec3 multiScatter ) {
vec2 fab = DFGApprox( normal, viewDir, roughness );
vec3 FssEss = specularColor * fab.x + specularF90 * fab.y;
float Ess = fab.x + fab.y;
float Ems = 1.0 - Ess;
vec3 Favg = specularColor + ( 1.0 - specularColor ) * 0.047619; // 1/21
vec3 Fms = FssEss * Favg / ( 1.0 - Ems * Favg );
singleScatter += FssEss;
multiScatter += Fms * Ems;
}
void RE_Direct_RectArea_Physical( const in RectAreaLight rectAreaLight, const in GeometricContext geometry, const in PhysicalMaterial material, inout ReflectedLight reflectedLight ) {
vec3 normal = geometry.normal;
vec3 viewDir = geometry.viewDir;
vec3 position = geometry.position;
vec3 lightPos = rectAreaLight.position;
vec3 halfWidth = rectAreaLight.halfWidth;
vec3 halfHeight = rectAreaLight.halfHeight;
vec3 lightColor = rectAreaLight.color;
float roughness = material.roughness;
vec3 rectCoords[ 4 ];
rectCoords[ 0 ] = lightPos + halfWidth - halfHeight; // counterclockwise; light shines in local neg z direction
rectCoords[ 1 ] = lightPos - halfWidth - halfHeight;
rectCoords[ 2 ] = lightPos - halfWidth + halfHeight;
rectCoords[ 3 ] = lightPos + halfWidth + halfHeight;
vec2 uv = LTC_Uv( normal, viewDir, roughness );
vec4 t1 = texture2D( ltc_1, uv );
vec4 t2 = texture2D( ltc_2, uv );
mat3 mInv = mat3(
vec3( t1.x, 0, t1.y ),
vec3( 0, 1, 0 ),
vec3( t1.z, 0, t1.w )
);
// LTC Fresnel Approximation by Stephen Hill
// http://blog.selfshadow.com/publications/s2016-advances/s2016_ltc_fresnel.pdf
vec3 fresnel = ( material.specularColor * t2.x + ( vec3( 1.0 ) - material.specularColor ) * t2.y );
reflectedLight.directSpecular += lightColor * fresnel * LTC_Evaluate( normal, viewDir, position, mInv, rectCoords );
reflectedLight.directDiffuse += lightColor * material.diffuseColor * LTC_Evaluate( normal, viewDir, position, mat3( 1.0 ), rectCoords );
}
void RE_Direct_Physical( const in IncidentLight directLight, const in GeometricContext geometry, const in PhysicalMaterial material, inout ReflectedLight reflectedLight ) {
float dotNL = saturate( dot( geometry.normal, directLight.direction ) );
vec3 irradiance = dotNL * directLight.color;
float dotNLcc = saturate( dot( geometry.clearcoatNormal, directLight.direction ) );
vec3 ccIrradiance = dotNLcc * directLight.color;
clearcoatSpecular += ccIrradiance * BRDF_GGX( directLight.direction, geometry.viewDir, geometry.clearcoatNormal, material.clearcoatF0, material.clearcoatF90, material.clearcoatRoughness );
sheenSpecular += irradiance * BRDF_Sheen( directLight.direction, geometry.viewDir, geometry.normal, material.sheenColor, material.sheenRoughness );
reflectedLight.directSpecular += irradiance * BRDF_GGX( directLight.direction, geometry.viewDir, geometry.normal, material.specularColor, material.specularF90, material.roughness );
reflectedLight.directDiffuse += irradiance * BRDF_Lambert( material.diffuseColor );
}
void RE_IndirectDiffuse_Physical( const in vec3 irradiance, const in GeometricContext geometry, const in PhysicalMaterial material, inout ReflectedLight reflectedLight ) {
reflectedLight.indirectDiffuse += irradiance * BRDF_Lambert( material.diffuseColor );
}
void RE_IndirectSpecular_Physical( const in vec3 radiance, const in vec3 irradiance, const in vec3 clearcoatRadiance, const in GeometricContext geometry, const in PhysicalMaterial material, inout ReflectedLight reflectedLight) {
clearcoatSpecular += clearcoatRadiance * EnvironmentBRDF( geometry.clearcoatNormal, geometry.viewDir, material.clearcoatF0, material.clearcoatF90, material.clearcoatRoughness );
sheenSpecular += irradiance * material.sheenColor * IBLSheenBRDF( geometry.normal, geometry.viewDir, material.sheenRoughness );
// Both indirect specular and indirect diffuse light accumulate here
vec3 singleScattering = vec3( 0.0 );
vec3 multiScattering = vec3( 0.0 );
vec3 cosineWeightedIrradiance = irradiance * RECIPROCAL_PI;
computeMultiscattering( geometry.normal, geometry.viewDir, material.specularColor, material.specularF90, material.roughness, singleScattering, multiScattering );
vec3 diffuse = material.diffuseColor * ( 1.0 - ( singleScattering + multiScattering ) );
reflectedLight.indirectSpecular += radiance * singleScattering;
reflectedLight.indirectSpecular += multiScattering * cosineWeightedIrradiance;
reflectedLight.indirectDiffuse += diffuse * cosineWeightedIrradiance;
}
// ref: https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
float computeSpecularOcclusion( const in float dotNV, const in float ambientOcclusion, const in float roughness ) {
return saturate( pow( dotNV + ambientOcclusion, exp2( - 16.0 * roughness - 1.0 ) ) - 1.0 + ambientOcclusion );
}
`;