Shaders: Fix iridescence IBL multiscattering and transposed XYZ_TO_REC709. (#33984)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/nodes/functions/PhysicalLightingModel.js

@@ -189,9 +189,9 @@ const getIBLVolumeRefraction = /*@__PURE__*/ Fn( ( [ n, v, roughness, diffuseCol
 
 // XYZ to linear-sRGB color space
 const XYZ_TO_REC709 = /*@__PURE__*/ mat3(
-	3.2404542, - 0.9692660, 0.0556434,
-	- 1.5371385, 1.8760108, - 0.2040259,
-	- 0.4985314, 0.0415560, 1.0572252
+	3.2404542, - 1.5371385, - 0.4985314,
+	- 0.9692660, 1.8760108, 0.0415560,
+	0.0556434, - 0.2040259, 1.0572252
 );
 
 // Assume air interface for top
@@ -457,14 +457,6 @@ class PhysicalLightingModel extends LightingModel {
 		 */
 		this.iridescenceFresnel = null;
 
-		/**
-		 * The iridescence F0.
-		 *
-		 * @type {?Node}
-		 * @default null
-		 */
-		this.iridescenceF0 = null;
-
 		/**
 		 * The iridescence F0 dielectric.
 		 *
@@ -531,8 +523,6 @@ class PhysicalLightingModel extends LightingModel {
 			this.iridescenceF0Dielectric = Schlick_to_F0( { f: iridescenceFresnelDielectric, f90: 1.0, dotVH: dotNVi } );
 			this.iridescenceF0Metallic = Schlick_to_F0( { f: iridescenceFresnelMetallic, f90: 1.0, dotVH: dotNVi } );
 
-			this.iridescenceF0 = mix( this.iridescenceF0Dielectric, this.iridescenceF0Metallic, metalness );
-
 		}
 
 		if ( this.transmission === true ) {

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

@@ -41,13 +41,14 @@ vec3 geometryClearcoatNormal = vec3( 0.0 );
 
 	if ( material.iridescence > 0.0 ) {
 
-		material.iridescenceFresnelDielectric = evalIridescence( 1.0, material.iridescenceIOR, dotNVi, material.iridescenceThickness, material.specularColor );
-		material.iridescenceFresnelMetallic = evalIridescence( 1.0, material.iridescenceIOR, dotNVi, material.iridescenceThickness, material.diffuseColor );
+		vec3 iridescenceFresnelDielectric = evalIridescence( 1.0, material.iridescenceIOR, dotNVi, material.iridescenceThickness, material.specularColor );
+		vec3 iridescenceFresnelMetallic = evalIridescence( 1.0, material.iridescenceIOR, dotNVi, material.iridescenceThickness, material.diffuseColor );
 
-		material.iridescenceFresnel = mix( material.iridescenceFresnelDielectric, material.iridescenceFresnelMetallic, material.metalness );
+		material.iridescenceFresnel = mix( iridescenceFresnelDielectric, iridescenceFresnelMetallic, material.metalness );
 
 		// Iridescence F0 approximation
-		material.iridescenceF0 = Schlick_to_F0( material.iridescenceFresnel, 1.0, dotNVi );
+		material.iridescenceF0Dielectric = Schlick_to_F0( iridescenceFresnelDielectric, 1.0, dotNVi );
+		material.iridescenceF0Metallic = Schlick_to_F0( iridescenceFresnelMetallic, 1.0, dotNVi );
 
 	}
 

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

@@ -30,9 +30,8 @@ struct PhysicalMaterial {
 		float iridescenceIOR;
 		float iridescenceThickness;
 		vec3 iridescenceFresnel;
-		vec3 iridescenceF0;
-		vec3 iridescenceFresnelDielectric;
-		vec3 iridescenceFresnelMetallic;
+		vec3 iridescenceF0Dielectric;
+		vec3 iridescenceF0Metallic;
 	#endif
 
 	#ifdef USE_SHEEN
@@ -589,8 +588,8 @@ void RE_IndirectSpecular_Physical( const in vec3 radiance, const in vec3 irradia
 
 	#ifdef USE_IRIDESCENCE
 
-		computeMultiscatteringIridescence( geometryNormal, geometryViewDir, material.specularColor, material.specularF90, material.iridescence, material.iridescenceFresnelDielectric, material.roughness, singleScatteringDielectric, multiScatteringDielectric );
-		computeMultiscatteringIridescence( geometryNormal, geometryViewDir, material.diffuseColor, material.specularF90, material.iridescence, material.iridescenceFresnelMetallic, material.roughness, singleScatteringMetallic, multiScatteringMetallic );
+		computeMultiscatteringIridescence( geometryNormal, geometryViewDir, material.specularColor, material.specularF90, material.iridescence, material.iridescenceF0Dielectric, material.roughness, singleScatteringDielectric, multiScatteringDielectric );
+		computeMultiscatteringIridescence( geometryNormal, geometryViewDir, material.diffuseColor, material.specularF90, material.iridescence, material.iridescenceF0Metallic, material.roughness, singleScatteringMetallic, multiScatteringMetallic );
 
 	#else