GLTFLoader: Clean up normalScale workaround. (#22584)

examples/jsm/loaders/GLTFLoader.js

@@ -692,8 +692,7 @@ class GLTFMaterialsClearcoatExtension {
 
 				const scale = extension.clearcoatNormalTexture.scale;
 
-				// https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
-				materialParams.clearcoatNormalScale = new Vector2( scale, - scale );
+				materialParams.clearcoatNormalScale = new Vector2( scale, scale );
 
 			}
 
@@ -2920,7 +2919,7 @@ class GLTFParser {
 		const geometry = mesh.geometry;
 		let material = mesh.material;
 
-		const useVertexTangents = geometry.attributes.tangent !== undefined;
+		const useDerivativeTangents = geometry.attributes.tangent === undefined;
 		const useVertexColors = geometry.attributes.color !== undefined;
 		const useFlatShading = geometry.attributes.normal === undefined;
 
@@ -2965,12 +2964,12 @@ class GLTFParser {
 		}
 
 		// Clone the material if it will be modified
-		if ( useVertexTangents || useVertexColors || useFlatShading ) {
+		if ( useDerivativeTangents || useVertexColors || useFlatShading ) {
 
 			let cacheKey = 'ClonedMaterial:' + material.uuid + ':';
 
 			if ( material.isGLTFSpecularGlossinessMaterial ) cacheKey += 'specular-glossiness:';
-			if ( useVertexTangents ) cacheKey += 'vertex-tangents:';
+			if ( useDerivativeTangents ) cacheKey += 'derivative-tangents:';
 			if ( useVertexColors ) cacheKey += 'vertex-colors:';
 			if ( useFlatShading ) cacheKey += 'flat-shading:';
 
@@ -2983,7 +2982,7 @@ class GLTFParser {
 				if ( useVertexColors ) cachedMaterial.vertexColors = true;
 				if ( useFlatShading ) cachedMaterial.flatShading = true;
 
-				if ( useVertexTangents ) {
+				if ( useDerivativeTangents ) {
 
 					// https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
 					if ( cachedMaterial.normalScale ) cachedMaterial.normalScale.y *= - 1;
@@ -3130,12 +3129,13 @@ class GLTFParser {
 
 			pending.push( parser.assignTexture( materialParams, 'normalMap', materialDef.normalTexture ) );
 
-			// https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
-			materialParams.normalScale = new Vector2( 1, - 1 );
+			materialParams.normalScale = new Vector2( 1, 1 );
 
 			if ( materialDef.normalTexture.scale !== undefined ) {
 
-				materialParams.normalScale.set( materialDef.normalTexture.scale, - materialDef.normalTexture.scale );
+				const scale = materialDef.normalTexture.scale;
+
+				materialParams.normalScale.set( scale, scale );
 
 			}