Merge pull request #10833 from donmccurdy/feat-gltf-2.0-meshes

[glTF] Update node and mesh loading for glTF 2.0.

examples/js/loaders/GLTF2Loader.js

@@ -1594,7 +1594,7 @@ THREE.GLTF2Loader = ( function () {
 
 							var attributeEntry = attributes[ attributeId ];
 
-							if ( ! attributeEntry ) return;
+							if ( attributeEntry === undefined ) return;
 
 							var bufferAttribute = dependencies.accessors[ attributeEntry ];
 
@@ -1923,11 +1923,25 @@ THREE.GLTF2Loader = ( function () {
 
 					var node = json.nodes[ nodeId ];
 
-					if ( node.meshes !== undefined ) {
+					var meshes;
+
+					if ( node.mesh !== undefined) {
+
+						meshes = [ node.mesh ];
+
+					} else if ( node.meshes !== undefined ) {
+
+						console.warn( 'GLTF2Loader: Legacy glTF file detected. Nodes may have no more than 1 mesh.' );
+
+						meshes = node.meshes;
+
+					}
+
+					if ( meshes !== undefined ) {
 
-						for ( var meshId in node.meshes ) {
+						for ( var meshId in meshes ) {
 
-							var mesh = node.meshes[ meshId ];
+							var mesh = meshes[ meshId ];
 							var group = dependencies.meshes[ mesh ];
 
 							if ( group === undefined ) {