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WebGLRenderer: Add energy conservation to sheen layer. #32147

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WebGLRenderer: Add energy conservation to sheen layer. #32147

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WebGLRenderer: Add energy conservation to sheen layer.
mrdoob Oct 30, 2025
4cf8b62
Updated screenshot.
mrdoob Oct 30, 2025
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44 changes: 40 additions & 4 deletions src/renderers/shaders/ShaderChunk/lights_physical_pars_fragment.glsl.js
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Expand Up @@ -530,6 +530,22 @@ void RE_Direct_Physical( const in IncidentLight directLight, const in vec3 geome

sheenSpecularDirect += irradiance * BRDF_Sheen( directLight.direction, geometryViewDir, geometryNormal, material.sheenColor, material.sheenRoughness );

// Energy conservation: reduce base layers by sheen energy
float dotNV = saturate( dot( geometryNormal, geometryViewDir ) );
float maxSheenColor = max( max( material.sheenColor.r, material.sheenColor.g ), material.sheenColor.b );

// Approximate directional albedo
float x = 1.0 - dotNV;
float r = material.sheenRoughness;
float r2 = r * r;
float baseAlbedo = 0.04 + 0.96 * r2;
float fresnelFactor = pow( x, 5.0 * ( 1.0 - r ) );
float E_sheen = baseAlbedo * mix( 1.0, fresnelFactor, 1.0 - r2 * r );

// Scale base layers
float sheenScaling = 1.0 - maxSheenColor * E_sheen;
irradiance *= sheenScaling;

#endif

reflectedLight.directSpecular += irradiance * BRDF_GGX_Multiscatter( directLight.direction, geometryViewDir, geometryNormal, material );
Expand All @@ -555,6 +571,20 @@ void RE_IndirectSpecular_Physical( const in vec3 radiance, const in vec3 irradia

sheenSpecularIndirect += irradiance * material.sheenColor * IBLSheenBRDF( geometryNormal, geometryViewDir, material.sheenRoughness );

// Energy conservation for indirect lighting
float dotNV = saturate( dot( geometryNormal, geometryViewDir ) );
float maxSheenColor = max( max( material.sheenColor.r, material.sheenColor.g ), material.sheenColor.b );

// Approximate directional albedo (same as direct lighting)
float x = 1.0 - dotNV;
float r = material.sheenRoughness;
float r2 = r * r;
float baseAlbedo = 0.04 + 0.96 * r2;
float fresnelFactor = pow( x, 5.0 * ( 1.0 - r ) );
float E_sheen = baseAlbedo * mix( 1.0, fresnelFactor, 1.0 - r2 * r );

float sheenScaling = 1.0 - maxSheenColor * E_sheen;

#endif

// Both indirect specular and indirect diffuse light accumulate here
Expand All @@ -576,10 +606,16 @@ void RE_IndirectSpecular_Physical( const in vec3 radiance, const in vec3 irradia
vec3 totalScattering = singleScattering + multiScattering;
vec3 diffuse = material.diffuseColor * ( 1.0 - max( max( totalScattering.r, totalScattering.g ), totalScattering.b ) );

reflectedLight.indirectSpecular += radiance * singleScattering;
reflectedLight.indirectSpecular += multiScattering * cosineWeightedIrradiance;

reflectedLight.indirectDiffuse += diffuse * cosineWeightedIrradiance;
#ifdef USE_SHEEN
// Apply energy conservation scaling to base layers
reflectedLight.indirectSpecular += radiance * singleScattering * sheenScaling;
reflectedLight.indirectSpecular += multiScattering * cosineWeightedIrradiance * sheenScaling;
reflectedLight.indirectDiffuse += diffuse * cosineWeightedIrradiance * sheenScaling;
#else
reflectedLight.indirectSpecular += radiance * singleScattering;
reflectedLight.indirectSpecular += multiScattering * cosineWeightedIrradiance;
reflectedLight.indirectDiffuse += diffuse * cosineWeightedIrradiance;
#endif

}

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