WebGLRenderer: Implement Sheen LUT

src/renderers/WebGLRenderer.js

@@ -55,6 +55,7 @@ import { WebGLUniformsGroups } from './webgl/WebGLUniformsGroups.js';
 import { createCanvasElement, probeAsync, warnOnce, error, warn, log } from '../utils.js';
 import { ColorManagement } from '../math/ColorManagement.js';
 import { getDFGLUT } from './shaders/DFGLUTData.js';
+import { getSheenLUT } from './shaders/SheenLUTData.js';
 
 /**
  * This renderer uses WebGL 2 to display scenes.
@@ -2520,6 +2521,13 @@ class WebGLRenderer {
 
 			}
 
+			// Set Sheen LUT for sheen materials
+			if ( material.sheen > 0 ) {
+
+				m_uniforms.sheenLUT.value = getSheenLUT();
+
+			}
+
 			if ( refreshMaterial ) {
 
 				p_uniforms.setValue( _gl, 'toneMappingExposure', _this.toneMappingExposure );

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

@@ -1,6 +1,7 @@
 export default /* glsl */`
 
 uniform sampler2D dfgLUT;
+uniform sampler2D sheenLUT;
 
 struct PhysicalMaterial {
 
@@ -530,6 +531,21 @@ void RE_Direct_Physical( const in IncidentLight directLight, const in vec3 geome
 
 		sheenSpecularDirect += irradiance * BRDF_Sheen( directLight.direction, geometryViewDir, geometryNormal, material.sheenColor, material.sheenRoughness );
 
+		float dotNV = saturate( dot( geometryNormal, geometryViewDir ) );
+		float maxSheenColor = max( max( material.sheenColor.r, material.sheenColor.g ), material.sheenColor.b );
+
+		// Lookup directional albedo for both view and light angles
+		float E_sheen_V = texture2D( sheenLUT, vec2( dotNV, material.sheenRoughness ) ).r;
+		float E_sheen_L = texture2D( sheenLUT, vec2( dotNL, material.sheenRoughness ) ).r;
+
+		// Take minimum for proper energy conservation
+		float sheenScaling = min(
+			1.0 - maxSheenColor * E_sheen_V,
+			1.0 - maxSheenColor * E_sheen_L
+		);
+
+		irradiance *= sheenScaling;
+
 	#endif
 
 	reflectedLight.directSpecular += irradiance * BRDF_GGX_Multiscatter( directLight.direction, geometryViewDir, geometryNormal, material );
@@ -555,6 +571,15 @@ 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 );
+
+		// Lookup directional albedo from LUT
+		float E_sheen = texture2D( sheenLUT, vec2( dotNV, material.sheenRoughness ) ).r;
+
+		float sheenScaling = 1.0 - maxSheenColor * E_sheen;
+
 	#endif
 
 	// Both indirect specular and indirect diffuse light accumulate here
@@ -576,10 +601,16 @@ 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
 
 }
 

src/renderers/shaders/UniformsLib.js

@@ -16,7 +16,9 @@ const UniformsLib = {
 		alphaMap: { value: null },
 		alphaMapTransform: { value: /*@__PURE__*/ new Matrix3() },
 
-		alphaTest: { value: 0 }
+		alphaTest: { value: 0 },
+
+		sheenLUT: { value: null }
 
 	},