diff --git a/lib/loadObj.js b/lib/loadObj.js
index eb8b464..b547be5 100644
--- a/lib/loadObj.js
+++ b/lib/loadObj.js
@@ -9,12 +9,20 @@ var loadMtl = require('./loadMtl');
 var readLines = require('./readLines');
 
 var Axis = Cesium.Axis;
+var Cartesian2 = Cesium.Cartesian2;
 var Cartesian3 = Cesium.Cartesian3;
 var ComponentDatatype = Cesium.ComponentDatatype;
 var defaultValue = Cesium.defaultValue;
 var defined = Cesium.defined;
+var IntersectionTests = Cesium.IntersectionTests;
+var Matrix3 = Cesium.Matrix3;
 var Matrix4 = Cesium.Matrix4;
+var OrientedBoundingBox = Cesium.OrientedBoundingBox;
+var Plane = Cesium.Plane;
+var PolygonPipeline = Cesium.PolygonPipeline;
+var Ray = Cesium.Ray;
 var RuntimeError = Cesium.RuntimeError;
+var WindingOrder = Cesium.WindingOrder;
 
 module.exports = loadObj;
 
@@ -137,6 +145,80 @@ function loadObj(objPath, options) {
         primitive.material = getName(name);
     }
 
+    var intPoint = new Cartesian3();
+    var xAxis = Cesium.Cartesian3.UNIT_X.clone();
+    var yAxis = Cesium.Cartesian3.UNIT_Y.clone();
+    var zAxis = Cesium.Cartesian3.UNIT_Z.clone();
+    var origin = new Cartesian3();
+    var normal = new Cartesian3();
+    var ray = new Ray();
+    var plane = new Plane(Cesium.Cartesian3.UNIT_X, 0);
+    function projectTo2D(positions) {
+        var positions2D = new Array(positions.length);
+        var obb = OrientedBoundingBox.fromPoints(positions);
+        var halfAxes = obb.halfAxes;
+        Matrix3.getColumn(halfAxes, 0, xAxis);
+        Matrix3.getColumn(halfAxes, 1, yAxis);
+        Matrix3.getColumn(halfAxes, 2, zAxis);
+
+        var xMag = Cartesian3.magnitude(xAxis);
+        var yMag = Cartesian3.magnitude(yAxis);
+        var zMag = Cartesian3.magnitude(zAxis);
+        var min = Math.min(xMag, yMag, zMag);
+
+        var center = obb.center;
+        var planeXAxis;
+        var planeYAxis;
+        if (min === xMag) {
+            if (!xAxis.equals(Cartesian3.ZERO)) {
+                Cartesian3.add(center, xAxis, origin);
+                Cartesian3.normalize(xAxis, normal);
+            }
+            planeXAxis = Cartesian3.normalize(yAxis, yAxis);
+            planeYAxis = Cartesian3.normalize(zAxis, zAxis);
+        } else if (min === yMag) {
+            if (!yAxis.equals(Cartesian3.ZERO)) {
+                Cartesian3.add(center, yAxis, origin);
+                Cartesian3.normalize(yAxis, normal);
+            }
+            planeXAxis = Cartesian3.normalize(xAxis, xAxis);
+            planeYAxis = Cartesian3.normalize(zAxis, zAxis);
+        } else {
+            if (!zAxis.equals(Cartesian3.ZERO)) {
+                Cartesian3.add(center, zAxis, origin);
+                Cartesian3.normalize(zAxis, normal);
+            }
+            planeXAxis = Cartesian3.normalize(xAxis, xAxis);
+            planeYAxis = Cartesian3.normalize(yAxis, yAxis);
+        }
+
+        if (min === 0) {
+            normal = Cartesian3.cross(planeXAxis, planeYAxis, normal);
+            normal = Cartesian3.normalize(normal, normal);
+        }
+
+        Plane.fromPointNormal(origin, normal, plane);
+        ray.direction = normal;
+
+        for (var i = 0; i < positions.length; i++) {
+            ray.origin = positions[i];
+
+            var intersectionPoint = IntersectionTests.rayPlane(ray, plane, intPoint);
+
+            if (!defined(intersectionPoint)) {
+                Cartesian3.negate(ray.direction, ray.direction);
+                intersectionPoint = IntersectionTests.rayPlane(ray, plane, intPoint);
+            }
+            var v = Cartesian3.subtract(intersectionPoint, origin, intersectionPoint);
+            var x = Cartesian3.dot(planeXAxis, v);
+            var y = Cartesian3.dot(planeYAxis, v);
+
+            positions2D[i] = new Cartesian2(x, y);
+        }
+
+        return positions2D;
+    }
+
     function getOffset(a, attributeData, components) {
         var i = parseInt(a);
         if (i < 0) {
@@ -199,45 +281,63 @@ function loadObj(objPath, options) {
 
     function addFace(vertices, positions, uvs, normals) {
 
-        var u1, u2, u3, u4, n1, n2, n3, n4;
+        var u1, u2, u3, n1, n2, n3;
 
-        var v1 = vertices[0];
-        var v2 = vertices[1];
-        var v3 = vertices[2];
-        var v4 = vertices[3];
-        var p1 = positions[0];
-        var p2 = positions[1];
-        var p3 = positions[2];
-        var p4 = positions[3];
+        if (vertices.length === 3) {
 
-        if (uvs) {
-            u1 = uvs[0];
-            u2 = uvs[1];
-            u3 = uvs[2];
-            u4 = uvs[3];
-        }
+            if (uvs) {
+                u1 = uvs[0];
+                u2 = uvs[1];
+                u3 = uvs[2];
+            }
 
-        if (normals) {
-            n1 = normals[0];
-            n2 = normals[1];
-            n3 = normals[2];
-            n4 = normals[3];
-        }
+            if (normals) {
+                n1 = normals[0];
+                n2 = normals[1];
+                n3 = normals[2];
+            }
 
-        var index1 = addVertex(v1, p1, u1, n1);
-        var index2 = addVertex(v2, p2, u2, n2);
-        var index3 = addVertex(v3, p3, u3, n3);
+            var index1 = addVertex(vertices[0], positions[0], u1, n1);
+            var index2 = addVertex(vertices[1], positions[1], u2, n2);
+            var index3 = addVertex(vertices[2], positions[2], u3, n3);
 
-        primitive.indices.push(index1);
-        primitive.indices.push(index2);
-        primitive.indices.push(index3);
-
-        // Triangulate if the face is a quad
-        if (defined(v4)) {
-            var index4 = addVertex(v4, p4, u4, n4);
             primitive.indices.push(index1);
+            primitive.indices.push(index2);
             primitive.indices.push(index3);
-            primitive.indices.push(index4);
+        } else { // Triangulate if the face is not a triangle
+            var positions3D = [];
+            var vertexIndices = [];
+
+            var i;
+            for (i=0; i < vertices.length; ++i) {
+                var u = (defined(uvs)) ? uvs[i] : undefined;
+                var n = (defined(normals)) ? normals[i] : undefined;
+
+                var index = addVertex(vertices[i], positions[i], u, n);
+                vertexIndices.push(index);
+
+                var pi = getOffset(index+1, positions, 3);
+                var px = mesh.positions.get(pi + 0);
+                var py = mesh.positions.get(pi + 1);
+                var pz = mesh.positions.get(pi + 2);
+
+                positions3D.push(new Cartesian3(px, py, pz));
+            }
+            var positions2D = projectTo2D(positions3D);
+
+            var windingOrder = PolygonPipeline.computeWindingOrder2D(positions2D);
+
+            // Since the projection doesn't respect winding order, reverse the order of
+            // the vertices before triangulating to enforce counter clockwise.
+            if (windingOrder === WindingOrder.CLOCKWISE) {
+                positions2D.reverse();
+            }
+
+            var positionIndices = PolygonPipeline.triangulate(positions2D);
+
+            for (i=0; i < positionIndices.length; ++i) {
+                primitive.indices.push(vertexIndices[positionIndices[i]]);
+            }
         }
 
     }
@@ -285,47 +385,39 @@ function loadObj(objPath, options) {
         } else if ((result = uvPattern.exec(line)) !== null) {
             uvs.push(parseFloat(result[1]));
             uvs.push(1.0 - parseFloat(result[2])); // Flip y so 0.0 is the bottom of the image
-        } else if (facePattern1.test(line)) { // format "f v v v ..."
-            var faceVertices = line.replace(faceSpaceOrSlashPattern, ' ').substring(1).split(' '); // get vertices
-            addFace(faceVertices, faceVertices, undefined, undefined);
-        } else if (facePattern2.test(line)) { // format "f v/uv v/uv v/uv ..."
+        } else {
             var faceVertices = line.replace(faceSpacePattern, ' ').substring(1).split(' '); // get vertex data (attributes '/' separated)
             var faceAttributes = line.replace(faceSpaceOrSlashPattern, ' ').substring(1).split(' '); // get vertex attributes
-
-            var facePositions = [];
-            var faceUvs = [];
-            for (var i=0; i <= faceAttributes.length - 2; i += 2)
-            {
-                facePositions.push(faceAttributes[i]);
-                faceUvs.push(faceAttributes[i+1]);
-            }
-            addFace(faceVertices, facePositions, faceUvs, undefined);
-        } else if (facePattern3.test(line)) { // format "v/uv/n v/uv/n v/uv/n ..."
-            var faceVertices = line.replace(faceSpacePattern, ' ').substring(1).split(' '); // get vertex data (attributes '/' separated)
-            var faceAttributes = line.replace(faceSpaceOrSlashPattern, ' ').substring(1).split(' '); // get vertex attributes
-
             var facePositions = [];
             var faceUvs = [];
             var faceNormals = [];
-            for (var i=0; i <= faceAttributes.length - 3; i += 3)
-            {
-                facePositions.push(faceAttributes[i]);
-                faceUvs.push(faceAttributes[i+1]);
-                faceNormals.push(faceAttributes[i+2]);
-            }
-            addFace(faceVertices, facePositions, faceUvs, faceNormals);
-        } else if (facePattern4.test(line)) { // format "v//n v//n v//n ..."
-            var faceVertices = line.replace(faceSpacePattern, ' ').substring(1).split(' '); // get vertex data (attributes '/' separated)
-            var faceAttributes = line.replace(faceSpaceOrSlashPattern, ' ').substring(1).split(' '); // get vertex attributes
 
-            var facePositions = [];
-            var faceNormals = [];
-            for (var i=0; i <= faceAttributes.length - 2; i += 2)
-            {
-                facePositions.push(faceAttributes[i]);
-                faceNormals.push(faceAttributes[i+1]);
+            if (facePattern1.test(line)) { // format "f v v v ..."
+                addFace(faceVertices, faceAttributes, undefined, undefined);
+            } else if (facePattern2.test(line)) { // format "f v/uv v/uv v/uv ..."
+                var i;
+                for (i=0; i <= faceAttributes.length - 2; i += 2)
+                {
+                    facePositions.push(faceAttributes[i]);
+                    faceUvs.push(faceAttributes[i+1]);
+                }
+                addFace(faceVertices, facePositions, faceUvs, undefined);
+            } else if (facePattern3.test(line)) { // format "v/uv/n v/uv/n v/uv/n ..."
+                for (i=0; i <= faceAttributes.length - 3; i += 3)
+                {
+                    facePositions.push(faceAttributes[i]);
+                    faceUvs.push(faceAttributes[i+1]);
+                    faceNormals.push(faceAttributes[i+2]);
+                }
+                addFace(faceVertices, facePositions, faceUvs, faceNormals);
+            } else if (facePattern4.test(line)) { // format "v//n v//n v//n ..."
+                for (i=0; i <= faceAttributes.length - 2; i += 2)
+                {
+                    facePositions.push(faceAttributes[i]);
+                    faceNormals.push(faceAttributes[i+1]);
+                }
+                addFace(faceVertices, facePositions, undefined, faceNormals);
             }
-            addFace(faceVertices, facePositions, undefined, faceNormals);
         }
     }
 
diff --git a/specs/data/box-triangles/box-triangles.mtl b/specs/data/box-triangles/box-triangles.mtl
index abbc294..70d3ba1 100644
--- a/specs/data/box-triangles/box-triangles.mtl
+++ b/specs/data/box-triangles/box-triangles.mtl
@@ -1,12 +1,10 @@
-# Blender MTL File: 'box.blend'
+# Blender MTL File: 'None'
 # Material Count: 1
 
-newmtl Material
-Ns 96.078431
+newmtl None
+Ns 0
 Ka 0.000000 0.000000 0.000000
-Kd 0.640000 0.640000 0.640000
-Ks 0.500000 0.500000 0.500000
-Ke 0.000000 0.000000 0.000000
-Ni 1.000000
-d 1.000000
+Kd 0.8 0.8 0.8
+Ks 0.8 0.8 0.8
+d 1
 illum 2
diff --git a/specs/data/box-triangles/box-triangles.obj b/specs/data/box-triangles/box-triangles.obj
index 124ab2d..b97f0d4 100644
--- a/specs/data/box-triangles/box-triangles.obj
+++ b/specs/data/box-triangles/box-triangles.obj
@@ -1,7 +1,7 @@
-# Blender v2.78 (sub 0) OBJ File: 'box.blend'
+# Blender v2.78 (sub 0) OBJ File: ''
 # www.blender.org
 mtllib box-triangles.mtl
-o Cube
+o Cube_Cube.001
 v -1.000000 -1.000000 1.000000
 v -1.000000 1.000000 1.000000
 v -1.000000 -1.000000 -1.000000
@@ -10,37 +10,23 @@ 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
-usemtl Material
+usemtl None
 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
+f 2//1 3//1 1//1
+f 4//2 7//2 3//2
+f 8//3 5//3 7//3
+f 6//4 1//4 5//4
+f 7//5 1//5 3//5
+f 4//6 6//6 8//6
+f 2//1 4//1 3//1
+f 4//2 8//2 7//2
+f 8//3 6//3 5//3
+f 6//4 2//4 1//4
+f 7//5 5//5 1//5
+f 4//6 2//6 6//6
diff --git a/specs/data/concave/concave.mtl b/specs/data/concave/concave.mtl
new file mode 100644
index 0000000..70d3ba1
--- /dev/null
+++ b/specs/data/concave/concave.mtl
@@ -0,0 +1,10 @@
+# Blender MTL File: 'None'
+# Material Count: 1
+
+newmtl None
+Ns 0
+Ka 0.000000 0.000000 0.000000
+Kd 0.8 0.8 0.8
+Ks 0.8 0.8 0.8
+d 1
+illum 2
diff --git a/specs/data/concave/concave.obj b/specs/data/concave/concave.obj
new file mode 100644
index 0000000..aeb002d
--- /dev/null
+++ b/specs/data/concave/concave.obj
@@ -0,0 +1,30 @@
+# Blender v2.78 (sub 0) OBJ File: ''
+# www.blender.org
+mtllib concave.mtl
+o Plane
+v -1.458150 0.363522 1.000000
+v 0.541850 0.363522 1.000000
+v -1.458150 0.363522 -1.000000
+v 0.541850 0.363522 -1.000000
+v -0.336510 0.363522 0.000000
+v -1.458150 -0.363522 1.000000
+v 0.541850 -0.363522 1.000000
+v -1.458150 -0.363522 -1.000000
+v 0.541850 -0.363522 -1.000000
+v -0.336510 -0.363522 0.000000
+vn 0.0000 1.0000 0.0000
+vn 0.0000 -1.0000 0.0000
+vn 0.7513 0.0000 -0.6599
+vn 0.7513 0.0000 0.6599
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl None
+s off
+f 1//1 2//1 5//1 4//1 3//1
+f 6//2 8//2 9//2 10//2 7//2
+f 2//3 7//3 10//3 5//3
+f 5//4 10//4 9//4 4//4
+f 3//5 8//5 6//5 1//5
+f 4//6 9//6 8//6 3//6
+f 1//7 6//7 7//7 2//7
diff --git a/specs/lib/loadObjSpec.js b/specs/lib/loadObjSpec.js
index ca7d2a7..a43930d 100644
--- a/specs/lib/loadObjSpec.js
+++ b/specs/lib/loadObjSpec.js
@@ -19,6 +19,7 @@ var objTrianglesUrl = 'specs/data/box-triangles/box-triangles.obj';
 var objObjectsUrl = 'specs/data/box-objects/box-objects.obj';
 var objGroupsUrl = 'specs/data/box-groups/box-groups.obj';
 var objObjectsGroupsUrl = 'specs/data/box-objects-groups/box-objects-groups.obj';
+var objConcaveUrl = 'specs/data/concave/concave.obj';
 var objUsemtlUrl = 'specs/data/box-usemtl/box-usemtl.obj';
 var objNoMaterialsUrl = 'specs/data/box-no-materials/box-no-materials.obj';
 var objMultipleMaterialsUrl = 'specs/data/box-multiple-materials/box-multiple-materials.obj';
@@ -196,6 +197,16 @@ describe('loadObj', function() {
             }), done).toResolve();
     });
 
+    it('loads obj with concave face containing 5 vertices', function(done) {
+        expect(loadObj(objConcaveUrl, defaultOptions)
+            .then(function(data) {
+                var mesh = getMeshes(data)[0];
+                var primitive = getPrimitives(data)[0];
+                expect(mesh.positions.length / 3).toBe(30);
+                expect(primitive.indices.length).toBe(48);
+            }), done).toResolve();
+    });
+
     it('loads obj with usemtl only', function(done) {
         expect(loadObj(objUsemtlUrl, defaultOptions)
             .then(function(data) {