GLTFLoader: add KHR_materials_emissive_strength (#23867)

* GLTFLoader: add KHR_materials_emissive_strength

* only set emissiveIntensity if emissiveStrength is defined

Co-authored-by: Don McCurdy <[email protected]>

Co-authored-by: Don McCurdy <[email protected]>

examples/jsm/loaders/GLTFLoader.js

@@ -117,6 +117,12 @@ class GLTFLoader extends Loader {
 
 		} );
 
+		this.register( function ( parser ) {
+
+			return new GLTFMaterialsEmissiveStrengthExtension( parser );
+
+		} );
+
 		this.register( function ( parser ) {
 
 			return new GLTFMaterialsSpecularExtension( parser );
@@ -453,6 +459,7 @@ const EXTENSIONS = {
 	KHR_TEXTURE_BASISU: 'KHR_texture_basisu',
 	KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
 	KHR_MESH_QUANTIZATION: 'KHR_mesh_quantization',
+	KHR_MATERIALS_EMISSIVE_STRENGTH: 'KHR_materials_emissive_strength',
 	EXT_TEXTURE_WEBP: 'EXT_texture_webp',
 	EXT_MESHOPT_COMPRESSION: 'EXT_meshopt_compression'
 };
@@ -638,6 +645,45 @@ class GLTFMaterialsUnlitExtension {
 
 }
 
+/**
+ * Materials Emissive Strength Extension
+ *
+ * Specification: https://github.com/KhronosGroup/glTF/blob/5768b3ce0ef32bc39cdf1bef10b948586635ead3/extensions/2.0/Khronos/KHR_materials_emissive_strength/README.md
+ */
+ class GLTFMaterialsEmissiveStrengthExtension {
+
+	constructor( parser ) {
+
+		this.parser = parser;
+		this.name = EXTENSIONS.KHR_MATERIALS_EMISSIVE_STRENGTH;
+
+	}
+
+	extendMaterialParams( materialIndex, materialParams ) {
+
+		const parser = this.parser;
+		const materialDef = parser.json.materials[ materialIndex ];
+
+		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
+
+			return Promise.resolve();
+
+		}
+
+		const emissiveStrength = materialDef.extensions[this.name].emissiveStrength;
+		
+		if ( emissiveStrength !== undefined ) {
+
+			materialParams.emissiveIntensity = emissiveStrength;
+
+		}
+
+		return Promise.resolve();
+
+	}
+
+}
+
 /**
  * Clearcoat Materials Extension
  *
@@ -1733,7 +1779,7 @@ class GLTFMaterialsPbrSpecularGlossinessExtension {
 		material.aoMapIntensity = 1.0;
 
 		material.emissive = materialParams.emissive;
-		material.emissiveIntensity = 1.0;
+		material.emissiveIntensity = materialParams.emissiveIntensity === undefined ? 1.0 : materialParams.emissiveIntensity;
 		material.emissiveMap = materialParams.emissiveMap === undefined ? null : materialParams.emissiveMap;
 
 		material.bumpMap = materialParams.bumpMap === undefined ? null : materialParams.bumpMap;