Set default material if usemtl is missing

lib/loadObj.js

@@ -525,6 +525,7 @@ function finishLoading(nodes, mtlPaths, objPath, options) {
     var name = path.basename(objPath, path.extname(objPath));
     return loadMtls(mtlPaths, objPath, options)
         .then(function(materials) {
+            assignDefaultMaterial(nodes, materials);
             return {
                 nodes : nodes,
                 materials : materials,
@@ -578,6 +579,26 @@ function loadMtls(mtlPaths, objPath, options) {
         });
 }
 
+function assignDefaultMaterial(nodes, materials) {
+    if (materials.length === 0) {
+        return;
+    }
+    var defaultMaterial = materials[0].name;
+    var nodesLength = nodes.length;
+    for (var i = 0; i < nodesLength; ++i) {
+        var meshes = nodes[i].meshes;
+        var meshesLength = meshes.length;
+        for (var j = 0; j < meshesLength; ++j) {
+            var primitives = meshes[j].primitives;
+            var primitivesLength = primitives.length;
+            for (var k = 0; k < primitivesLength; ++k) {
+                var primitive = primitives[k];
+                primitive.material = defaultValue(primitive.material, defaultMaterial);
+            }
+        }
+    }
+}
+
 function removeEmptyMeshes(meshes) {
     return meshes.filter(function(mesh) {
         // Remove empty primitives

specs/data/box-missing-usemtl/box-missing-usemtl.mtl

@@ -0,0 +1,12 @@
+# Blender MTL File: 'None'
+# Material Count: 1
+
+newmtl Material
+Ns 96.078431
+Ka 0.100000 0.000000 0.000000
+Kd 0.640000 0.640000 0.640000
+Ks 0.500000 0.500000 0.500000
+Ke 0.000000 0.000000 0.100000
+Ni 1.000000
+d 1.000000
+illum 2

specs/data/box-missing-usemtl/box-missing-usemtl.obj

@@ -0,0 +1,45 @@
+# Blender v2.78 (sub 0) OBJ File: ''
+# www.blender.org
+mtllib box-missing-usemtl.mtl
+o Cube
+v -1.000000 -1.000000 1.000000
+v -1.000000 1.000000 1.000000
+v -1.000000 -1.000000 -1.000000
+v -1.000000 1.000000 -1.000000
+v 1.000000 -1.000000 1.000000
+v 1.000000 1.000000 1.000000
+v 1.000000 -1.000000 -1.000000
+v 1.000000 1.000000 -1.000000
+vt 0.0000 0.0000
+vt 1.0000 0.0000
+vt 1.0000 1.0000
+vt 0.0000 1.0000
+vt 0.0000 0.0000
+vt 1.0000 0.0000
+vt 1.0000 1.0000
+vt 0.0000 1.0000
+vt 0.0000 0.0000
+vt 1.0000 0.0000
+vt 1.0000 1.0000
+vt 0.0000 1.0000
+vt 0.0000 0.0000
+vt 1.0000 0.0000
+vt 1.0000 1.0000
+vt 0.0000 1.0000
+vt 1.0000 0.0000
+vt 1.0000 1.0000
+vt 0.0000 0.0000
+vt 0.0000 1.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 0.0000 1.0000
+vn 0.0000 -1.0000 0.0000
+vn 0.0000 1.0000 0.0000
+s off
+f 1/1/1 2/2/1 4/3/1 3/4/1
+f 3/5/2 4/6/2 8/7/2 7/8/2
+f 7/9/3 8/10/3 6/11/3 5/12/3
+f 5/13/4 6/14/4 2/15/4 1/16/4
+f 3/5/5 7/17/5 5/18/5 1/16/5
+f 8/19/6 4/6/6 2/15/6 6/20/6

specs/lib/loadObjSpec.js

@@ -25,6 +25,7 @@ var objUncleanedPath = 'specs/data/box-uncleaned/box-uncleaned.obj';
 var objMtllibPath = 'specs/data/box-mtllib/box-mtllib.obj';
 var objMtllibSpacesPath = 'specs/data/box-mtllib-spaces/box mtllib.obj';
 var objMissingMtllibPath = 'specs/data/box-missing-mtllib/box-missing-mtllib.obj';
+var objMissingUsemtlPath = 'specs/data/box-missing-usemtl/box-missing-usemtl.obj';
 var objExternalResourcesPath = 'specs/data/box-external-resources/box-external-resources.obj';
 var objResourcesInRootPath = 'specs/data/box-resources-in-root/box-resources-in-root.obj';
 var objExternalResourcesInRootPath = 'specs/data/box-external-resources-in-root/box-external-resources-in-root.obj';
@@ -363,6 +364,14 @@ describe('loadObj', function() {
             }), done).toResolve();
     });
 
+    it('loads obj with missing usemtl', function(done) {
+        expect(loadObj(objMissingUsemtlPath, options)
+            .then(function(data) {
+                expect(data.materials.length).toBe(1);
+                expect(data.nodes[0].meshes[0].primitives[0].material).toBe('Material');
+            }), done).toResolve();
+    });
+
     it('loads .mtl outside of the obj directory', function(done) {
         expect(loadObj(objExternalResourcesPath, options)
             .then(function(data) {