WebGLRenderer/WebGPURenderer: Improve Physical Accuracy (#32330)

Author: mrdoob

src/nodes/functions/BSDF/V_GGX_SmithCorrelated_Anisotropic.js

@@ -9,7 +9,7 @@ const V_GGX_SmithCorrelated_Anisotropic = /*@__PURE__*/ Fn( ( { alphaT, alphaB,
 	const gl = dotNV.mul( vec3( alphaT.mul( dotTL ), alphaB.mul( dotBL ), dotNL ).length() );
 	const v = div( 0.5, gv.add( gl ) );
 
-	return v.saturate();
+	return v;
 
 } ).setLayout( {
 	name: 'V_GGX_SmithCorrelated_Anisotropic',

src/nodes/functions/PhysicalLightingModel.js

@@ -751,7 +751,7 @@ class PhysicalLightingModel extends LightingModel {
 		// Diffuse energy conservation uses dielectric path
 		const totalScatteringDielectric = singleScatteringDielectric.add( multiScatteringDielectric );
 
-		const diffuse = diffuseContribution.mul( totalScatteringDielectric.r.max( totalScatteringDielectric.g ).max( totalScatteringDielectric.b ).oneMinus() );
+		const diffuse = diffuseContribution.mul( totalScatteringDielectric.oneMinus() );
 
 		const cosineWeightedIrradiance = iblIrradiance.mul( 1 / Math.PI );
 

src/renderers/shaders/ShaderChunk/lights_physical_pars_fragment.glsl.js

@@ -71,12 +71,10 @@ vec3 Schlick_to_F0( const in vec3 f, const in float f90, const in float dotVH )
     return ( f - vec3( f90 ) * x5 ) / ( 1.0 - x5 );
 }
 
-// Moving Frostbite to Physically Based Rendering 3.0 - page 12, listing 2
-// https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
+// Heitz 2014, "Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs"
 float V_GGX_SmithCorrelated( const in float alpha, const in float dotNL, const in float dotNV ) {
 
 	float a2 = pow2( alpha );
-
 	float gv = dotNL * sqrt( a2 + ( 1.0 - a2 ) * pow2( dotNV ) );
 	float gl = dotNV * sqrt( a2 + ( 1.0 - a2 ) * pow2( dotNL ) );
 
@@ -106,7 +104,7 @@ float D_GGX( const in float alpha, const in float dotNH ) {
 		float gl = dotNV * length( vec3( alphaT * dotTL, alphaB * dotBL, dotNL ) );
 		float v = 0.5 / ( gv + gl );
 
-		return saturate(v);
+		return v;
 
 	}
 
@@ -463,7 +461,7 @@ vec3 BRDF_GGX_Multiscatter( const in vec3 lightDir, const in vec3 viewDir, const
 	vec3 Favg = material.specularColorBlended + ( 1.0 - material.specularColorBlended ) * 0.047619; // 1/21
 
 	// Multiple scattering contribution
-	vec3 Fms = FssEss_V * FssEss_L * Favg / ( 1.0 - Ems_V * Ems_L * Favg * Favg + EPSILON );
+	vec3 Fms = FssEss_V * FssEss_L * Favg / ( 1.0 - Ems_V * Ems_L * Favg + EPSILON );
 
 	// Energy compensation factor
 	float compensationFactor = Ems_V * Ems_L;
@@ -590,7 +588,7 @@ void RE_IndirectSpecular_Physical( const in vec3 radiance, const in vec3 irradia
 
 	// Diffuse energy conservation uses dielectric path
 	vec3 totalScatteringDielectric = singleScatteringDielectric + multiScatteringDielectric;
-	vec3 diffuse = material.diffuseContribution * ( 1.0 - max( max( totalScatteringDielectric.r, totalScatteringDielectric.g ), totalScatteringDielectric.b ) );
+	vec3 diffuse = material.diffuseContribution * ( 1.0 - totalScatteringDielectric );
 
 	vec3 cosineWeightedIrradiance = irradiance * RECIPROCAL_PI;