GLTFExporter: Add sheen and emission strength export. (#25346)

* added sheen and emission strength export

* removed emissive warning

examples/jsm/exporters/GLTFExporter.js

@@ -114,6 +114,18 @@ class GLTFExporter {
 
 		} );
 
+		this.register( function ( writer ) {
+
+			return new GLTFMaterialsSheenExtension( writer );
+
+		} );
+
+		this.register( function ( writer ) {
+
+			return new GLTFMaterialsEmissiveStrengthExtension( writer );
+
+		} );
+
 	}
 
 	register( callback ) {
@@ -1410,7 +1422,7 @@ class GLTFWriter {
 
 		}
 
-		// pbrMetallicRoughness.baseColorTexture or pbrSpecularGlossiness diffuseTexture
+		// pbrMetallicRoughness.baseColorTexture
 		if ( material.map ) {
 
 			const baseColorMapDef = { index: this.processTexture( material.map ) };
@@ -1421,21 +1433,12 @@ class GLTFWriter {
 
 		if ( material.emissive ) {
 
-			// note: emissive components are limited to stay within the 0 - 1 range to accommodate glTF spec. see #21849 and #22000.
-			const emissive = material.emissive.clone().multiplyScalar( material.emissiveIntensity );
+			const emissive = material.emissive;
 			const maxEmissiveComponent = Math.max( emissive.r, emissive.g, emissive.b );
 
-			if ( maxEmissiveComponent > 1 ) {
-
-				emissive.multiplyScalar( 1 / maxEmissiveComponent );
-
-				console.warn( 'THREE.GLTFExporter: Some emissive components exceed 1; emissive has been limited' );
-
-			}
-
 			if ( maxEmissiveComponent > 0 ) {
 
-				materialDef.emissiveFactor = emissive.toArray();
+				materialDef.emissiveFactor = material.emissive.toArray();
 
 			}
 
@@ -2712,8 +2715,8 @@ class GLTFMaterialsSpecularExtension {
 
 	writeMaterial( material, materialDef ) {
 
-		if ( ! material.isMeshPhysicalMaterial || ( material.specularIntensity === 1.0 && 
-		       material.specularColor.equals( DEFAULT_SPECULAR_COLOR ) && 
+		if ( ! material.isMeshPhysicalMaterial || ( material.specularIntensity === 1.0 &&
+		       material.specularColor.equals( DEFAULT_SPECULAR_COLOR ) &&
 		     ! material.specularIntensityMap && ! material.specularColorTexture ) ) return;
 
 		const writer = this.writer;
@@ -2749,6 +2752,91 @@ class GLTFMaterialsSpecularExtension {
 
 }
 
+/**
+ * Sheen Materials Extension
+ *
+ * Specification: https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_sheen
+ */
+class GLTFMaterialsSheenExtension {
+
+	constructor( writer ) {
+
+		this.writer = writer;
+		this.name = 'KHR_materials_sheen';
+
+	}
+
+	writeMaterial( material, materialDef ) {
+
+		if ( ! material.isMeshPhysicalMaterial || material.sheen == 0.0 ) return;
+
+		const writer = this.writer;
+		const extensionsUsed = writer.extensionsUsed;
+
+		const extensionDef = {};
+
+		if ( material.sheenRoughnessMap ) {
+
+			const sheenRoughnessMapDef = { index: writer.processTexture( material.sheenRoughnessMap ) };
+			writer.applyTextureTransform( sheenRoughnessMapDef, material.sheenRoughnessMap );
+			extensionDef.sheenRoughnessTexture = sheenRoughnessMapDef;
+
+		}
+
+		if ( material.sheenColorMap ) {
+
+			const sheenColorMapDef = { index: writer.processTexture( material.sheenColorMap ) };
+			writer.applyTextureTransform( sheenColorMapDef, material.sheenColorMap );
+			extensionDef.sheenColorTexture = sheenColorMapDef;
+
+		}
+
+		extensionDef.sheenRoughnessFactor = material.sheenRoughness;
+		extensionDef.sheenColorFactor = material.sheenColor.toArray();
+
+		materialDef.extensions = materialDef.extensions || {};
+		materialDef.extensions[ this.name ] = extensionDef;
+
+		extensionsUsed[ this.name ] = true;
+
+	}
+
+}
+
+/**
+ * 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( writer ) {
+
+		this.writer = writer;
+		this.name = 'KHR_materials_emissive_strength';
+
+	}
+
+	writeMaterial( material, materialDef ) {
+
+		if ( ! material.isMeshStandardMaterial || material.emissiveIntensity === 1.0 ) return;
+
+		const writer = this.writer;
+		const extensionsUsed = writer.extensionsUsed;
+
+		const extensionDef = {};
+
+		extensionDef.emissiveStrength = material.emissiveIntensity;
+
+		materialDef.extensions = materialDef.extensions || {};
+		materialDef.extensions[ this.name ] = extensionDef;
+
+		extensionsUsed[ this.name ] = true;
+
+	}
+
+}
+
 /**
  * Static utility functions
  */