diff --git a/demo/dev.html b/demo/dev.html
index 174e3d2d..5531339d 100644
--- a/demo/dev.html
+++ b/demo/dev.html
@@ -30,6 +30,7 @@ <h1>Matter.js Demo (Dev. Build)</h1>
             <div class="controls-container">
                 <select id="demo-select">
                     <option value="mixed">Mixed Shapes</option>
+                    <option value="concave">Concave Shapes</option>
                     <option value="mixedSolid">Solid Rendering</option>
                     <option value="newtonsCradle">Newton's Cradle</option>
                     <option value="wreckingBall">Wrecking Ball</option>
diff --git a/demo/js/Demo.js b/demo/js/Demo.js
index f9bd0ead..d78dc0f8 100644
--- a/demo/js/Demo.js
+++ b/demo/js/Demo.js
@@ -114,7 +114,55 @@
 
         World.add(_world, stack);
         
-        var renderOptions = _engine.render.options;
+        var renderOptions = _engine.render.options;
+    };
+
+    Demo.concave = function() {
+        var _world = _engine.world;
+
+        Demo.reset();
+
+        var s = 50;
+        //var vertices = [{ x: 0, y: 0 }, { x: 0, y: 2 * s }, 
+        //                { x: 1 * s, y: 2 * s }, { x: 1 * s, y: 1 * s },
+        //                { x: 2 * s, y: 1 * s }, { x: 2 * s, y: 0 }];
+
+        //var vertices = Matter.Vertices.fromPath('-5 78,70 126,57 195,114 139,191 201,161 136,217 83,151 83,122 -1,82 85');
+
+        var partA = Bodies.rectangle(200, 200, 200, 20);
+        var partB = Bodies.rectangle(200, 200, 20, 200);
+        var middle = Bodies.rectangle(200, 200, 20, 20);
+        //var parent = Bodies.rectangle(200, 200, 200, 200);
+
+        var vertices = Matter.Vertices.create(partA.vertices.concat(partB.vertices.concat(middle.vertices)), true);
+        Matter.Vertices.clockwiseSort(vertices);
+
+        //debugger;
+
+        var hull = Matter.Vertices.hull(vertices);
+
+        console.log(vertices);
+        console.log(hull);
+
+        var parent = Body.create({
+            position: { x: 200, y: 200 },
+            vertices: hull
+        });
+
+        //debugger;
+
+        partA.parent = parent;
+        partB.parent = parent;
+
+        parent.parts = [parent, partA, partB];
+
+        World.add(_world, parent);
+
+        _world.gravity.y = 0;
+        
+        var renderOptions = _engine.render.options;
+        renderOptions.showCollisions = true;
+        renderOptions.showBounds = true;
     };
 
     Demo.slingshot = function() {
diff --git a/src/body/Body.js b/src/body/Body.js
index 1166c0bc..14ec51f4 100644
--- a/src/body/Body.js
+++ b/src/body/Body.js
@@ -116,7 +116,8 @@ var Body = {};
             anglePrev: body.anglePrev || body.angle,
             vertices: body.vertices,
             isStatic: body.isStatic,
-            isSleeping: body.isSleeping
+            isSleeping: body.isSleeping,
+            parts: body.parts || [body]
         });
 
         Vertices.rotate(body.vertices, body.angle, body.position);
@@ -313,6 +314,8 @@ var Body = {};
 
         Vertices.translate(body.vertices, delta);
         Bounds.update(body.bounds, body.vertices, body.velocity);
+
+        //Common.each(body.children, Body.setPosition, position);
     };
 
     /**
@@ -330,6 +333,8 @@ var Body = {};
         Vertices.rotate(body.vertices, delta, body.position);
         Axes.rotate(body.axes, delta);
         Bounds.update(body.bounds, body.vertices, body.velocity);
+
+        //Common.each(body.children, Body.setAngle, angle);
     };
 
     /**
@@ -439,12 +444,15 @@ var Body = {};
         body.angularSpeed = Math.abs(body.angularVelocity);
 
         // transform the body geometry
-        Vertices.translate(body.vertices, body.velocity);
-        if (body.angularVelocity !== 0) {
-            Vertices.rotate(body.vertices, body.angularVelocity, body.position);
-            Axes.rotate(body.axes, body.angularVelocity);
+        for (var i = 0; i < body.parts.length; i++) {
+            var part = body.parts[i];
+            Vertices.translate(part.vertices, body.velocity);
+            if (body.angularVelocity !== 0) {
+                Vertices.rotate(part.vertices, body.angularVelocity, body.position);
+                Axes.rotate(part.axes, body.angularVelocity);
+            }
+            Bounds.update(part.bounds, body.vertices, body.velocity);
         }
-        Bounds.update(body.bounds, body.vertices, body.velocity);
     };
 
     /**
diff --git a/src/collision/Detector.js b/src/collision/Detector.js
index 0577cf81..701aec86 100644
--- a/src/collision/Detector.js
+++ b/src/collision/Detector.js
@@ -41,33 +41,43 @@ var Detector = {};
 
             // mid phase
             if (Bounds.overlaps(bodyA.bounds, bodyB.bounds)) {
-
-                // find a previous collision we could reuse
-                var pairId = Pair.id(bodyA, bodyB),
-                    pair = pairsTable[pairId],
-                    previousCollision;
-
-                if (pair && pair.isActive) {
-                    previousCollision = pair.collision;
-                } else {
-                    previousCollision = null;
-                }
-
-                // narrow phase
-                var collision = SAT.collides(bodyA, bodyB, previousCollision);
-
-                // @if DEBUG
-                metrics.narrowphaseTests += 1;
-                if (collision.reused)
-                    metrics.narrowReuseCount += 1;
-                // @endif
-
-                if (collision.collided) {
-                    collisions.push(collision);
-                    // @if DEBUG
-                    metrics.narrowDetections += 1;
-                    // @endif
-                }
+               /*for (var j = 1; j < bodyA.parts.length; j++) {
+                    var partA = bodyA.parts[j];
+
+                    for (var k = 1; k < bodyB.parts.length; k++) {
+                        var partB = bodyB.parts[k];
+
+                        if (Bounds.overlaps(partA.bounds, partB.bounds)) {*/
+
+                            // find a previous collision we could reuse
+                            var pairId = Pair.id(bodyA, bodyB),
+                                pair = pairsTable[pairId],
+                                previousCollision;
+
+                            if (pair && pair.isActive) {
+                                previousCollision = pair.collision;
+                            } else {
+                                previousCollision = null;
+                            }
+
+                            // narrow phase
+                            var collision = SAT.collides(bodyA, bodyB, previousCollision);
+
+                            // @if DEBUG
+                            metrics.narrowphaseTests += 1;
+                            if (collision.reused)
+                                metrics.narrowReuseCount += 1;
+                            // @endif
+
+                            if (collision.collided) {
+                                collisions.push(collision);
+                                // @if DEBUG
+                                metrics.narrowDetections += 1;
+                                // @endif
+                            }
+                       //}
+                    //}
+                //}
             }
         }
 
diff --git a/src/collision/Resolver.js b/src/collision/Resolver.js
index ca243aca..9be4543c 100644
--- a/src/collision/Resolver.js
+++ b/src/collision/Resolver.js
@@ -98,8 +98,11 @@ var Resolver = {};
                 body.positionPrev.y += body.positionImpulse.y;
 
                 // update body geometry
-                Vertices.translate(body.vertices, body.positionImpulse);
-                Bounds.update(body.bounds, body.vertices, body.velocity);
+                for (var j = 0; j < body.parts.length; j++) {
+                    var part = body.parts[j];
+                    Vertices.translate(part.vertices, body.positionImpulse);
+                    Bounds.update(part.bounds, body.vertices, body.velocity);
+                }
                 
                 // dampen accumulator to warm the next step
                 body.positionImpulse.x *= _positionWarming;
diff --git a/src/constraint/Constraint.js b/src/constraint/Constraint.js
index d35b9bee..3a8371e2 100644
--- a/src/constraint/Constraint.js
+++ b/src/constraint/Constraint.js
@@ -249,15 +249,18 @@ var Constraint = {};
                 impulse = body.constraintImpulse;
 
             // update geometry and reset
-            Vertices.translate(body.vertices, impulse);
+            for (var j = 0; j < body.parts.length; j++) {
+                var part = body.parts[j];
+                Vertices.translate(part.vertices, impulse);
 
-            if (impulse.angle !== 0) {
-                Vertices.rotate(body.vertices, impulse.angle, body.position);
-                Axes.rotate(body.axes, impulse.angle);
-                impulse.angle = 0;
-            }
+                if (impulse.angle !== 0) {
+                    Vertices.rotate(part.vertices, impulse.angle, body.position);
+                    Axes.rotate(part.axes, impulse.angle);
+                    impulse.angle = 0;
+                }
 
-            Bounds.update(body.bounds, body.vertices);
+                Bounds.update(part.bounds, body.vertices);
+            }
 
             impulse.x = 0;
             impulse.y = 0;
diff --git a/src/geometry/Vector.js b/src/geometry/Vector.js
index 54c5fd47..d8b02ce9 100644
--- a/src/geometry/Vector.js
+++ b/src/geometry/Vector.js
@@ -122,6 +122,18 @@ var Vector = {};
         return (vectorA.x * vectorB.y) - (vectorA.y * vectorB.x);
     };
 
+    /**
+     * Returns the cross-product of three vectors.
+     * @method cross3
+     * @param {vector} vectorA
+     * @param {vector} vectorB
+     * @param {vector} vectorC
+     * @return {number} The cross product of the three vectors
+     */
+    Vector.cross3 = function(vectorA, vectorB, vectorC) {
+        return (vectorB.x - vectorA.x) * (vectorC.y - vectorA.y) - (vectorB.y - vectorA.y) * (vectorC.x - vectorA.x);
+    };
+
     /**
      * Adds the two vectors.
      * @method add
diff --git a/src/geometry/Vertices.js b/src/geometry/Vertices.js
index bc73bd81..ff84fd38 100644
--- a/src/geometry/Vertices.js
+++ b/src/geometry/Vertices.js
@@ -89,6 +89,23 @@ var Vertices = {};
         return Vector.div(centre, 6 * area);
     };
 
+    /**
+     * Returns the average (mean) of the set of vertices.
+     * @method mean
+     * @param {vertices} vertices
+     * @return {vector} The average point
+     */
+    Vertices.mean = function(vertices) {
+        var average = { x: 0, y: 0 };
+
+        for (var i = 0; i < vertices.length; i++) {
+            average.x += vertices[i].x;
+            average.y += vertices[i].y;
+        }
+
+        return Vector.div(average, vertices.length);
+    };
+
     /**
      * Returns the area of the set of vertices.
      * @method area
@@ -306,4 +323,73 @@ var Vertices = {};
         return newVertices;
     };
 
+    /**
+     * Sorts the input vertices into clockwise order in place.
+     * @method clockwiseSort
+     * @param {vertices} vertices
+     * @return {vertices} vertices
+     */
+    Vertices.clockwiseSort = function(vertices) {
+        var mean = Vertices.mean(vertices);
+
+        vertices.sort(function(vertexA, vertexB) {
+            return Vector.angle(mean, vertexA) - Vector.angle(mean, vertexB);
+        });
+
+        return vertices;
+    }
+
+    /**
+     * Returns the convex hull of the input vertices as a new array of points.
+     * @method hull
+     * @param {vertices} vertices
+     * @return [vertex] vertices
+     */
+    Vertices.hull = function(vertices) {
+        // http://en.wikibooks.org/wiki/Algorithm_Implementation/Geometry/Convex_hull/Monotone_chain
+
+        var upper = [],
+            lower = [], 
+            vertex,
+            i;
+
+        // sort vertices on x-axis (y-axis for ties)
+        vertices = vertices.slice(0);
+        vertices.sort(function(vertexA, vertexB) {
+            var dx = vertexA.x - vertexB.x;
+            return dx !== 0 ? dx : vertexA.y - vertexB.y;
+        });
+
+        // build lower hull
+        for (i = 0; i < vertices.length; i++) {
+            vertex = vertices[i];
+
+            while (lower.length >= 2 
+                   && Vector.cross3(lower[lower.length - 2], lower[lower.length - 1], vertex) <= 0) {
+                lower.pop();
+            }
+
+            lower.push(vertex);
+        }
+
+        // build upper hull
+        for (i = vertices.length - 1; i >= 0; i--) {
+            vertex = vertices[i];
+
+            while (upper.length >= 2 
+                   && Vector.cross3(upper[upper.length - 2], upper[upper.length - 1], vertex) <= 0) {
+                upper.pop();
+            }
+
+            upper.push(vertex);
+        }
+
+        // concatenation of the lower and upper hulls gives the convex hull
+        // omit last points because they are repeated at the beginning of the other list
+        upper.pop();
+        lower.pop();
+
+        return upper.concat(lower);
+    };
+
 })();
diff --git a/src/render/Render.js b/src/render/Render.js
index ce62bc6a..bc0c853c 100644
--- a/src/render/Render.js
+++ b/src/render/Render.js
@@ -448,14 +448,15 @@ var Render = {};
     Render.bodyWireframes = function(engine, bodies, context) {
         var c = context,
             i,
-            j;
+            j,
+            k;
 
         c.beginPath();
 
         for (i = 0; i < bodies.length; i++) {
             var body = bodies[i];
 
-            if (!body.render.visible)
+            if (!body.render.visible || body.parts.length === 1)
                 continue;
 
             c.moveTo(body.vertices[0].x, body.vertices[0].y);
@@ -467,6 +468,39 @@ var Render = {};
             c.lineTo(body.vertices[0].x, body.vertices[0].y);
         }
 
+        c.lineWidth = 1;
+        c.strokeStyle = '#9E9277';
+        c.stroke();
+
+        for (i = 0; i < bodies.length; i++) {
+            var body = bodies[i];
+            for (j = 0; j < body.vertices.length; j++) {
+                c.fillStyle = 'yellow';
+                c.fillText(j, body.vertices[j].x, body.vertices[j].y + 10);
+            }
+        }
+
+        c.beginPath();
+
+        for (i = 0; i < bodies.length; i++) {
+            var body = bodies[i];
+
+            if (!body.render.visible)
+                continue;
+
+            for (k = body.parts.length > 1 ? 1 : 0; k < body.parts.length; k++) {
+                var part = body.parts[k];
+
+                c.moveTo(part.vertices[0].x, part.vertices[0].y);
+
+                for (j = 1; j < part.vertices.length; j++) {
+                    c.lineTo(part.vertices[j].x, part.vertices[j].y);
+                }
+                
+                c.lineTo(part.vertices[0].x, part.vertices[0].y);
+            }
+        }
+
         c.lineWidth = 1;
         c.strokeStyle = '#bbb';
         c.stroke();