diff --git a/box2dbody.cpp b/box2dbody.cpp
index bc13e9a0..76c0a841 100644
--- a/box2dbody.cpp
+++ b/box2dbody.cpp
@@ -61,7 +61,7 @@ Box2DBody::Box2DBody(QQuickItem *parent) :
 Box2DBody::~Box2DBody()
 {
     if (mBody)
-        mWorld->DestroyBody(mBody);
+        mWorld->world().DestroyBody(mBody);
 }
 
 void Box2DBody::setLinearDamping(float linearDamping)
@@ -242,10 +242,10 @@ void Box2DBody::addFixture(Box2DFixture *fixture)
     fixture->setParentItem(this);
     mFixtures.append(fixture);
     if (mBody)
-        fixture->initialize(mBody);
+        fixture->initialize(this);
 }
 
-void Box2DBody::initialize(b2World *world)
+void Box2DBody::initialize(Box2DWorld *world)
 {
     mWorld = world;
     if (!isComponentComplete()) {
@@ -255,12 +255,12 @@ void Box2DBody::initialize(b2World *world)
         mInitializePending = true;
         return;
     }
-    mBodyDef.position = toMeters(position());
+    mBodyDef.position = mWorld->toMeters(position());
     mBodyDef.angle = toRadians(rotation());
-    mBody = world->CreateBody(&mBodyDef);
+    mBody = mWorld->world().CreateBody(&mBodyDef);
     mInitializePending = false;
     foreach (Box2DFixture *fixture, mFixtures)
-        fixture->initialize(mBody);
+        fixture->initialize(this);
     emit bodyCreated();
 }
 
@@ -273,7 +273,7 @@ void Box2DBody::synchronize()
     mSynchronizing = true;
 
     if (sync(mBodyDef.position, mBody->GetPosition())) {
-        setPosition(toPixels(mBodyDef.position));
+        setPosition(mWorld->toPixels(mBodyDef.position));
         emit positionChanged();
     }
 
@@ -296,7 +296,7 @@ void Box2DBody::geometryChanged(const QRectF &newGeometry,
 {
     if (!mSynchronizing && mBody) {
         if (newGeometry.topLeft() != oldGeometry.topLeft()) {
-            mBodyDef.position = toMeters(newGeometry.topLeft());
+            mBodyDef.position = mWorld->toMeters(newGeometry.topLeft());
             mBody->SetTransform(mBodyDef.position, mBodyDef.angle);
         }
     }
@@ -316,7 +316,7 @@ void Box2DBody::applyLinearImpulse(const QPointF &impulse,
                                    const QPointF &point)
 {
     if (mBody)
-        mBody->ApplyLinearImpulse(invertY(impulse), toMeters(point), true);
+        mBody->ApplyLinearImpulse(invertY(impulse), mWorld->toMeters(point), true);
 }
 
 void Box2DBody::applyAngularImpulse(qreal impulse)
@@ -334,14 +334,14 @@ void Box2DBody::applyTorque(qreal torque)
 QPointF Box2DBody::getWorldCenter() const
 {
     if (mBody)
-        return toPixels(mBody->GetWorldCenter());
+        return mWorld->toPixels(mBody->GetWorldCenter());
     return QPointF();
 }
 
 void Box2DBody::applyForce(const QPointF &force, const QPointF &point)
 {
     if (mBody)
-        mBody->ApplyForce(invertY(force), toMeters(point), true);
+        mBody->ApplyForce(invertY(force), mWorld->toMeters(point), true);
 }
 
 void Box2DBody::applyForceToCenter(const QPointF &force)
@@ -369,13 +369,13 @@ float Box2DBody::getInertia() const
 QPointF Box2DBody::getLinearVelocityFromWorldPoint(const QPointF &point) const
 {
     if (mBody)
-        return invertY(mBody->GetLinearVelocityFromWorldPoint(toMeters(point)));
+        return invertY(mBody->GetLinearVelocityFromWorldPoint(mWorld->toMeters(point)));
     return QPointF();
 }
 
 QPointF Box2DBody::getLinearVelocityFromLocalPoint(const QPointF &point) const
 {
     if (mBody)
-        return invertY(mBody->GetLinearVelocityFromLocalPoint(toMeters(point)));
+        return invertY(mBody->GetLinearVelocityFromLocalPoint(mWorld->toMeters(point)));
     return QPointF();
 }
diff --git a/box2dbody.h b/box2dbody.h
index 9e52db3e..26a27fe1 100644
--- a/box2dbody.h
+++ b/box2dbody.h
@@ -103,7 +103,7 @@ class Box2DBody : public QQuickItem
 
     QQmlListProperty<Box2DFixture> fixtures();
 
-    void initialize(b2World *world);
+    void initialize(Box2DWorld *world);
     void synchronize();
     void nullifyBody();
 
@@ -122,7 +122,7 @@ class Box2DBody : public QQuickItem
 
     void componentComplete();
     b2Body *body() const;
-    b2World *world() const;
+    Box2DWorld *world() const;
 
 protected:
     void geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry);
@@ -143,7 +143,7 @@ class Box2DBody : public QQuickItem
 
 private:
     b2Body *mBody;
-    b2World *mWorld;
+    Box2DWorld *mWorld;
     b2BodyDef mBodyDef;
     bool mSynchronizing;
     bool mInitializePending;
@@ -205,7 +205,7 @@ inline b2Body *Box2DBody::body() const
     return mBody;
 }
 
-inline b2World *Box2DBody::world() const
+inline Box2DWorld *Box2DBody::world() const
 {
     return mWorld;
 }
diff --git a/box2ddebugdraw.cpp b/box2ddebugdraw.cpp
index b1b0c733..9bc27929 100644
--- a/box2ddebugdraw.cpp
+++ b/box2ddebugdraw.cpp
@@ -34,7 +34,7 @@
 class DebugDraw : public b2Draw
 {
 public:
-    DebugDraw(QPainter *painter, b2World &world);
+    DebugDraw(QPainter *painter, Box2DWorld &world);
 
     void draw();
 
@@ -54,11 +54,11 @@ class DebugDraw : public b2Draw
 
 private:
     QPainter *mPainter;
-    b2World &mWorld;
+    Box2DWorld &mWorld;
     qreal mAxisScale;
 };
 
-DebugDraw::DebugDraw(QPainter *painter, b2World &world)
+DebugDraw::DebugDraw(QPainter *painter, Box2DWorld &world)
     : mPainter(painter)
     , mWorld(world)
 {
@@ -66,9 +66,9 @@ DebugDraw::DebugDraw(QPainter *painter, b2World &world)
 
 void DebugDraw::draw()
 {
-    mWorld.SetDebugDraw(this);
-    mWorld.DrawDebugData();
-    mWorld.SetDebugDraw(0);
+    mWorld.world().SetDebugDraw(this);
+    mWorld.world().DrawDebugData();
+    mWorld.world().SetDebugDraw(0);
 }
 
 static QColor toQColor(const b2Color &color)
@@ -79,13 +79,13 @@ static QColor toQColor(const b2Color &color)
                   color.a * 255);
 }
 
-static QPolygonF toQPolygonF(const b2Vec2 *vertices, int32 vertexCount)
+static QPolygonF toQPolygonF(const Box2DWorld &world, const b2Vec2 *vertices, int32 vertexCount)
 {
     QPolygonF polygon;
     polygon.reserve(vertexCount);
 
     for (int i = 0; i < vertexCount; ++i)
-        polygon.append(toPixels(vertices[i]));
+        polygon.append(world.toPixels(vertices[i]));
 
     return polygon;
 }
@@ -95,7 +95,7 @@ void DebugDraw::DrawPolygon(const b2Vec2 *vertices, int32 vertexCount,
 {
     mPainter->setPen(toQColor(color));
     mPainter->setBrush(Qt::NoBrush);
-    mPainter->drawPolygon(toQPolygonF(vertices, vertexCount));
+    mPainter->drawPolygon(toQPolygonF(mWorld, vertices, vertexCount));
 }
 
 void DebugDraw::DrawSolidPolygon(const b2Vec2 *vertices, int32 vertexCount,
@@ -103,7 +103,7 @@ void DebugDraw::DrawSolidPolygon(const b2Vec2 *vertices, int32 vertexCount,
 {
     mPainter->setPen(Qt::NoPen);
     mPainter->setBrush(toQColor(color));
-    mPainter->drawPolygon(toQPolygonF(vertices, vertexCount));
+    mPainter->drawPolygon(toQPolygonF(mWorld, vertices, vertexCount));
 }
 
 void DebugDraw::DrawCircle(const b2Vec2 &center, float32 radius,
@@ -111,9 +111,9 @@ void DebugDraw::DrawCircle(const b2Vec2 &center, float32 radius,
 {
     mPainter->setPen(toQColor(color));
     mPainter->setBrush(Qt::NoBrush);
-    mPainter->drawEllipse(toPixels(center),
-                          toPixels(radius),
-                          toPixels(radius));
+    mPainter->drawEllipse(mWorld.toPixels(center),
+                          mWorld.toPixels(radius),
+                          mWorld.toPixels(radius));
 }
 
 void DebugDraw::DrawSolidCircle(const b2Vec2 &center, float32 radius,
@@ -121,11 +121,11 @@ void DebugDraw::DrawSolidCircle(const b2Vec2 &center, float32 radius,
 {
     mPainter->setPen(Qt::NoPen);
     mPainter->setBrush(toQColor(color));
-    QPointF p1 = toPixels(center);
-    QPointF p2 = toPixels(axis);
+    QPointF p1 = mWorld.toPixels(center);
+    QPointF p2 = mWorld.toPixels(axis);
     mPainter->drawEllipse(p1,
-                          toPixels(radius),
-                          toPixels(radius));
+                          mWorld.toPixels(radius),
+                          mWorld.toPixels(radius));
     mPainter->setPen(qRgb(200, 64, 0));
     p2.setX(p1.x() + radius * p2.x());
     p2.setY(p1.y() + radius * p2.y());
@@ -136,20 +136,20 @@ void DebugDraw::DrawSegment(const b2Vec2 &p1, const b2Vec2 &p2,
                             const b2Color &color)
 {
     mPainter->setPen(toQColor(color));
-    mPainter->drawLine(toPixels(p1), toPixels(p2));
+    mPainter->drawLine(mWorld.toPixels(p1), mWorld.toPixels(p2));
 }
 
 void DebugDraw::DrawTransform(const b2Transform &xf)
 {
-    QPointF p1 = toPixels(xf.p);
-    QPointF p2 = toPixels(xf.q.GetXAxis());
+    QPointF p1 = mWorld.toPixels(xf.p);
+    QPointF p2 = mWorld.toPixels(xf.q.GetXAxis());
     p2 = QPointF(p1.x() + mAxisScale * p2.x(),
                  p1.y() + mAxisScale * p2.y());
 
     mPainter->setPen(Qt::blue); // X axis
     mPainter->drawLine(p1,p2);
 
-    p2 = toPixels(xf.q.GetYAxis());
+    p2 = mWorld.toPixels(xf.q.GetYAxis());
     p2 = QPointF(p1.x() + mAxisScale * p2.x(),
                  p1.y() + mAxisScale * p2.y());
 
@@ -210,7 +210,7 @@ void Box2DDebugDraw::paint(QPainter *p)
     if (!mWorld)
         return;
 
-    DebugDraw debugDraw(p, mWorld->world());
+    DebugDraw debugDraw(p, *mWorld);
     debugDraw.SetFlags(mFlags);
     debugDraw.setAxisScale(mAxisScale);
     debugDraw.draw();
diff --git a/box2ddistancejoint.cpp b/box2ddistancejoint.cpp
index 825632fd..f4ba2710 100644
--- a/box2ddistancejoint.cpp
+++ b/box2ddistancejoint.cpp
@@ -36,15 +36,15 @@ Box2DDistanceJoint::Box2DDistanceJoint(QObject *parent) :
 
 float Box2DDistanceJoint::length() const
 {
-    return toPixels(mDistanceJointDef.length);
+    return world()->toPixels(mDistanceJointDef.length);
 }
 
 void Box2DDistanceJoint::setLength(float length)
 {
-    if (mDistanceJointDef.length == toMeters(length))
+    if (mDistanceJointDef.length == world()->toMeters(length))
         return;
 
-    mDistanceJointDef.length = toMeters(length);
+    mDistanceJointDef.length = world()->toMeters(length);
     if (distanceJoint())
         distanceJoint()->SetLength(mDistanceJointDef.length);
     emit lengthChanged();
@@ -74,24 +74,24 @@ void Box2DDistanceJoint::setDampingRatio(float dampingRatio)
 
 QPointF Box2DDistanceJoint::localAnchorA() const
 {
-    return toPixels(mDistanceJointDef.localAnchorA);
+    return world()->toPixels(mDistanceJointDef.localAnchorA);
 }
 
 void Box2DDistanceJoint::setLocalAnchorA(const QPointF &localAnchorA)
 {
-    mDistanceJointDef.localAnchorA = toMeters(localAnchorA);
+    mDistanceJointDef.localAnchorA = world()->toMeters(localAnchorA);
     mAnchorsAuto = false;
     emit localAnchorBChanged();
 }
 
 QPointF Box2DDistanceJoint::localAnchorB() const
 {
-    return toPixels(mDistanceJointDef.localAnchorB);
+    return world()->toPixels(mDistanceJointDef.localAnchorB);
 }
 
 void Box2DDistanceJoint::setLocalAnchorB(const QPointF &localAnchorB)
 {
-    mDistanceJointDef.localAnchorB = toMeters(localAnchorB);
+    mDistanceJointDef.localAnchorB = world()->toMeters(localAnchorB);
     mAnchorsAuto = false;
     emit localAnchorBChanged();
 }
@@ -105,7 +105,7 @@ b2Joint *Box2DDistanceJoint::createJoint()
                                      mDistanceJointDef.bodyB->GetWorldCenter());
     }
 
-    return world()->CreateJoint(&mDistanceJointDef);
+    return world()->world().CreateJoint(&mDistanceJointDef);
 }
 
 QPointF Box2DDistanceJoint::getReactionForce(float32 inv_dt) const
diff --git a/box2dfixture.cpp b/box2dfixture.cpp
index 4c09abbf..aacfed0f 100644
--- a/box2dfixture.cpp
+++ b/box2dfixture.cpp
@@ -157,21 +157,21 @@ void Box2DFixture::setGroupIndex(int groupIndex)
     emit groupIndexChanged();
 }
 
-void Box2DFixture::initialize(b2Body *body)
+void Box2DFixture::initialize(Box2DBody *body)
 {
+    mBody = body;
     b2Shape *shape = createShape();
     if (!shape)
         return;
 
     mFixtureDef.shape = shape;
-    mFixture = body->CreateFixture(&mFixtureDef);
-    mBody = body;
+    mFixture = body->body()->CreateFixture(&mFixtureDef);
     delete shape;
 }
 
 Box2DBody *Box2DFixture::getBody() const
 {
-    return mBody ? toBox2DBody(mBody) : 0;
+    return mBody;
 }
 
 void Box2DFixture::recreateFixture()
@@ -179,7 +179,7 @@ void Box2DFixture::recreateFixture()
     if (!mBody)
         return;
     if (mFixture)
-        mBody->DestroyFixture(mFixture);
+        mBody->body()->DestroyFixture(mFixture);
     initialize(mBody);
 }
 
@@ -200,9 +200,9 @@ b2Shape *Box2DBox::createShape()
                          y() + halfHeight);
 
     b2PolygonShape *shape = new b2PolygonShape;
-    shape->SetAsBox(toMeters(halfWidth),
-                    toMeters(halfHeight),
-                    toMeters(center),
+    shape->SetAsBox(mBody->world()->toMeters(halfWidth),
+                    mBody->world()->toMeters(halfHeight),
+                    mBody->world()->toMeters(center),
                     toRadians(rotation()));
 
     return shape;
@@ -231,8 +231,8 @@ b2Shape *Box2DCircle::createShape()
 {
     b2CircleShape *shape = new b2CircleShape;
 
-    shape->m_radius = toMeters(mRadius);
-    shape->m_p = toMeters(position() + QPointF(mRadius, mRadius));
+    shape->m_radius = mBody->world()->toMeters(mRadius);
+    shape->m_p = mBody->world()->toMeters(position() + QPointF(mRadius, mRadius));
 
     return shape;
 }
@@ -260,7 +260,7 @@ b2Shape *Box2DPolygon::createShape()
     QScopedArrayPointer<b2Vec2> vertices(new b2Vec2[count]);
 
     for (int i = 0; i < count; ++i) {
-        vertices[i] = toMeters(mVertices.at(i).toPointF());
+        vertices[i] = mBody->world()->toMeters(mVertices.at(i).toPointF());
 
         if (i > 0) {
             if (b2DistanceSquared(vertices[i - 1], vertices[i]) <= b2_linearSlop * b2_linearSlop) {
@@ -340,7 +340,7 @@ b2Shape *Box2DChain::createShape()
     QScopedArrayPointer<b2Vec2> vertices(new b2Vec2[count]);
 
     for (int i = 0; i < count; ++i) {
-        vertices[i] = toMeters(mVertices.at(i).toPointF());
+        vertices[i] = mBody->world()->toMeters(mVertices.at(i).toPointF());
 
         if (i > 0) {
             if (b2DistanceSquared(vertices[i - 1], vertices[i]) <= b2_linearSlop * b2_linearSlop) {
@@ -357,9 +357,9 @@ b2Shape *Box2DChain::createShape()
         shape->CreateChain(vertices.data(), count);
 
         if (mPrevVertexFlag)
-            shape->SetPrevVertex(toMeters(mPrevVertex));
+            shape->SetPrevVertex(mBody->world()->toMeters(mPrevVertex));
         if (mNextVertexFlag)
-            shape->SetNextVertex(toMeters(mNextVertex));
+            shape->SetNextVertex(mBody->world()->toMeters(mNextVertex));
     }
 
     return shape;
@@ -384,8 +384,8 @@ b2Shape *Box2DEdge::createShape()
         qWarning() << "Edge: Invalid number of vertices:" << count;
         return 0;
     }
-    const b2Vec2 vertex1 = toMeters(mVertices.at(0).toPointF());
-    const b2Vec2 vertex2 = toMeters(mVertices.at(1).toPointF());
+    const b2Vec2 vertex1 = mBody->world()->toMeters(mVertices.at(0).toPointF());
+    const b2Vec2 vertex2 = mBody->world()->toMeters(mVertices.at(1).toPointF());
     if (b2DistanceSquared(vertex1, vertex2) <= b2_linearSlop * b2_linearSlop) {
         qWarning() << "Edge: vertices are too close together";
         return 0;
diff --git a/box2dfixture.h b/box2dfixture.h
index 4728ef62..9122dcd6 100644
--- a/box2dfixture.h
+++ b/box2dfixture.h
@@ -82,7 +82,7 @@ class Box2DFixture : public QQuickItem
     int groupIndex() const;
     void setGroupIndex(int groupIndex);
 
-    void initialize(b2Body *body);
+    void initialize(Box2DBody *body);
 
     Q_INVOKABLE Box2DBody *getBody() const;
 
@@ -105,7 +105,7 @@ class Box2DFixture : public QQuickItem
 
     b2Fixture *mFixture;
     b2FixtureDef mFixtureDef;
-    b2Body *mBody;
+    Box2DBody *mBody;
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(Box2DFixture::CategoryFlags)
diff --git a/box2dfrictionjoint.cpp b/box2dfrictionjoint.cpp
index 41dfc61f..d2222c77 100644
--- a/box2dfrictionjoint.cpp
+++ b/box2dfrictionjoint.cpp
@@ -67,13 +67,13 @@ void Box2DFrictionJoint::setMaxTorque(float maxTorque)
 QPointF Box2DFrictionJoint::localAnchorA() const
 {
     if (frictionJoint())
-        return toPixels(frictionJoint()->GetAnchorA());
-    return toPixels(mFrictionJointDef.localAnchorA);
+        return world()->toPixels(frictionJoint()->GetAnchorA());
+    return world()->toPixels(mFrictionJointDef.localAnchorA);
 }
 
 void Box2DFrictionJoint::setLocalAnchorA(const QPointF &localAnchorA)
 {
-    mFrictionJointDef.localAnchorA = toMeters(localAnchorA);
+    mFrictionJointDef.localAnchorA = world()->toMeters(localAnchorA);
     mAnchorsAuto = false;
     emit localAnchorAChanged();
 }
@@ -81,13 +81,13 @@ void Box2DFrictionJoint::setLocalAnchorA(const QPointF &localAnchorA)
 QPointF Box2DFrictionJoint::localAnchorB() const
 {
     if (frictionJoint())
-        return toPixels(frictionJoint()->GetAnchorB());
-    return toPixels(mFrictionJointDef.localAnchorB);
+        return world()->toPixels(frictionJoint()->GetAnchorB());
+    return world()->toPixels(mFrictionJointDef.localAnchorB);
 }
 
 void Box2DFrictionJoint::setLocalAnchorB(const QPointF &localAnchorB)
 {
-    mFrictionJointDef.localAnchorB = toMeters(localAnchorB);
+    mFrictionJointDef.localAnchorB = world()->toMeters(localAnchorB);
     mAnchorsAuto = false;
     emit localAnchorBChanged();
 }
@@ -100,7 +100,7 @@ b2Joint *Box2DFrictionJoint::createJoint()
                                      mFrictionJointDef.bodyA->GetWorldCenter());
     }
 
-    return world()->CreateJoint(&mFrictionJointDef);
+    return world()->world().CreateJoint(&mFrictionJointDef);
 }
 
 QPointF Box2DFrictionJoint::getReactionForce(float32 inv_dt) const
diff --git a/box2dgearjoint.cpp b/box2dgearjoint.cpp
index 8f4ac614..29310244 100644
--- a/box2dgearjoint.cpp
+++ b/box2dgearjoint.cpp
@@ -109,7 +109,7 @@ b2Joint *Box2DGearJoint::createJoint()
     mGearJointDef.joint1 = mJoint1->joint();
     mGearJointDef.joint2 = mJoint2->joint();
 
-    return world()->CreateJoint(&mGearJointDef);
+    return world()->world().CreateJoint(&mGearJointDef);
 }
 
 void Box2DGearJoint::joint1Created()
diff --git a/box2djoint.cpp b/box2djoint.cpp
index 2e0fddab..6f9f8ad2 100644
--- a/box2djoint.cpp
+++ b/box2djoint.cpp
@@ -24,7 +24,7 @@
  */
 
 #include "box2djoint.h"
-
+#include "box2dworld.h"
 #include "box2dbody.h"
 
 Box2DJoint::Box2DJoint(b2JointDef &jointDef, QObject *parent) :
@@ -42,7 +42,7 @@ Box2DJoint::Box2DJoint(b2JointDef &jointDef, QObject *parent) :
 Box2DJoint::~Box2DJoint()
 {
     if (mJoint)
-        mWorld->DestroyJoint(mJoint);
+        mWorld->world().DestroyJoint(mJoint);
 }
 
 void Box2DJoint::setCollideConnected(bool collideConnected)
@@ -96,7 +96,7 @@ void Box2DJoint::initialize()
 
     // Destroy any previously created joint
     if (mJoint) {
-        mWorld->DestroyJoint(mJoint);
+        mWorld->world().DestroyJoint(mJoint);
         mJoint = 0;
         mWorld = 0;
     }
diff --git a/box2djoint.h b/box2djoint.h
index fffea5a7..6fe1ec10 100644
--- a/box2djoint.h
+++ b/box2djoint.h
@@ -81,7 +81,7 @@ class Box2DJoint : public QObject, public QQmlParserStatus
     void initialize();
 
     void nullifyJoint();
-    b2World *world() const;
+    Box2DWorld *world() const;
     b2Joint *joint() const;
 
     // QQmlParserStatus interface
@@ -107,7 +107,7 @@ private slots:
     bool mInitializePending;
     Box2DBody *mBodyA;
     Box2DBody *mBodyB;
-    b2World *mWorld;
+    Box2DWorld *mWorld;
     b2Joint *mJoint;
 };
 
@@ -136,7 +136,7 @@ inline void Box2DJoint::nullifyJoint()
     mJoint = 0;
 }
 
-inline b2World *Box2DJoint::world() const
+inline Box2DWorld *Box2DJoint::world() const
 {
     return mWorld;
 }
diff --git a/box2dmotorjoint.cpp b/box2dmotorjoint.cpp
index 276d9ae1..079570ce 100644
--- a/box2dmotorjoint.cpp
+++ b/box2dmotorjoint.cpp
@@ -36,12 +36,12 @@ Box2DMotorJoint::Box2DMotorJoint(QObject *parent) :
 
 QPointF Box2DMotorJoint::linearOffset() const
 {
-    return toPixels(mMotorJointDef.linearOffset);
+    return world()->toPixels(mMotorJointDef.linearOffset);
 }
 
 void Box2DMotorJoint::setLinearOffset(const QPointF &linearOffset)
 {
-    const b2Vec2 linearOffsetMeters = toMeters(linearOffset);
+    const b2Vec2 linearOffsetMeters = world()->toMeters(linearOffset);
     if (mMotorJointDef.linearOffset == linearOffsetMeters)
         return;
 
@@ -105,5 +105,5 @@ b2Joint *Box2DMotorJoint::createJoint()
 {
     mMotorJointDef.Initialize(bodyA()->body(), bodyB()->body());
 
-    return world()->CreateJoint(&mMotorJointDef);
+    return world()->world().CreateJoint(&mMotorJointDef);
 }
diff --git a/box2dmousejoint.cpp b/box2dmousejoint.cpp
index 19619597..5cd4bc4e 100644
--- a/box2dmousejoint.cpp
+++ b/box2dmousejoint.cpp
@@ -68,12 +68,12 @@ void Box2DMouseJoint::setMaxForce(float maxForce)
 
 QPointF Box2DMouseJoint::target() const
 {
-    return toPixels(mMouseJointDef.target);
+    return world()->toPixels(mMouseJointDef.target);
 }
 
 void Box2DMouseJoint::setTarget(const QPointF &target)
 {
-    const b2Vec2 targetMeters = toMeters(target);
+    const b2Vec2 targetMeters = world()->toMeters(target);
     if (mMouseJointDef.target == targetMeters)
         return;
 
@@ -85,7 +85,7 @@ void Box2DMouseJoint::setTarget(const QPointF &target)
 
 b2Joint *Box2DMouseJoint::createJoint()
 {
-    return world()->CreateJoint(&mMouseJointDef);
+    return world()->world().CreateJoint(&mMouseJointDef);
 }
 
 QPointF Box2DMouseJoint::getReactionForce(float32 inv_dt) const
diff --git a/box2dprismaticjoint.cpp b/box2dprismaticjoint.cpp
index dbed1f9d..87ca0a73 100644
--- a/box2dprismaticjoint.cpp
+++ b/box2dprismaticjoint.cpp
@@ -36,12 +36,12 @@ Box2DPrismaticJoint::Box2DPrismaticJoint(QObject *parent) :
 
 float Box2DPrismaticJoint::lowerTranslation() const
 {
-    return toPixels(mPrismaticJointDef.lowerTranslation);
+    return world()->toPixels(mPrismaticJointDef.lowerTranslation);
 }
 
 void Box2DPrismaticJoint::setLowerTranslation(float lowerTranslation)
 {
-    const float lowerTranslationMeters = toMeters(lowerTranslation);
+    const float lowerTranslationMeters = world()->toMeters(lowerTranslation);
     if (mPrismaticJointDef.lowerTranslation == lowerTranslationMeters)
         return;
 
@@ -54,12 +54,12 @@ void Box2DPrismaticJoint::setLowerTranslation(float lowerTranslation)
 
 float Box2DPrismaticJoint::upperTranslation() const
 {
-    return toPixels(mPrismaticJointDef.upperTranslation);
+    return world()->toPixels(mPrismaticJointDef.upperTranslation);
 }
 
 void Box2DPrismaticJoint::setUpperTranslation(float upperTranslation)
 {
-    const float upperTranslationMeters = toMeters(upperTranslation);
+    const float upperTranslationMeters = world()->toMeters(upperTranslation);
     if (mPrismaticJointDef.upperTranslation == upperTranslationMeters)
         return;
 
@@ -122,7 +122,7 @@ void Box2DPrismaticJoint::setEnableMotor(bool enableMotor)
 
 QPointF Box2DPrismaticJoint::axis() const
 {
-    return toPixels(mPrismaticJointDef.localAxisA);
+    return world()->toPixels(mPrismaticJointDef.localAxisA);
 }
 
 void Box2DPrismaticJoint::setAxis(const QPointF &axis)
@@ -134,24 +134,24 @@ void Box2DPrismaticJoint::setAxis(const QPointF &axis)
 
 QPointF Box2DPrismaticJoint::localAnchorA() const
 {
-    return toPixels(mPrismaticJointDef.localAnchorA);
+    return world()->toPixels(mPrismaticJointDef.localAnchorA);
 }
 
 QPointF Box2DPrismaticJoint::localAnchorB() const
 {
-    return toPixels(mPrismaticJointDef.localAnchorB);
+    return world()->toPixels(mPrismaticJointDef.localAnchorB);
 }
 
 void Box2DPrismaticJoint::setLocalAnchorA(const QPointF &localAnchorA)
 {
-    mPrismaticJointDef.localAnchorA = toMeters(localAnchorA);
+    mPrismaticJointDef.localAnchorA = world()->toMeters(localAnchorA);
     mAnchorsAuto = false;
     emit localAnchorAChanged();
 }
 
 void Box2DPrismaticJoint::setLocalAnchorB(const QPointF &localAnchorB)
 {
-    mPrismaticJointDef.localAnchorB = toMeters(localAnchorB);
+    mPrismaticJointDef.localAnchorB = world()->toMeters(localAnchorB);
     mAnchorsAuto = false;
     emit localAnchorBChanged();
 }
@@ -167,13 +167,13 @@ b2Joint *Box2DPrismaticJoint::createJoint()
         mPrismaticJointDef.referenceAngle = 0.0;
     }
 
-    return world()->CreateJoint(&mPrismaticJointDef);
+    return world()->world().CreateJoint(&mPrismaticJointDef);
 }
 
 float Box2DPrismaticJoint::getJointTranslation() const
 {
     if (prismaticJoint())
-        return toPixels(prismaticJoint()->GetJointTranslation());
+        return world()->toPixels(prismaticJoint()->GetJointTranslation());
     return 0.0;
 }
 
diff --git a/box2dpulleyjoint.cpp b/box2dpulleyjoint.cpp
index 33944f2d..abee4d47 100644
--- a/box2dpulleyjoint.cpp
+++ b/box2dpulleyjoint.cpp
@@ -35,29 +35,29 @@ Box2DPulleyJoint::Box2DPulleyJoint(QObject *parent) :
 
 float Box2DPulleyJoint::lengthA() const
 {
-    return toPixels(mPulleyJointDef.lengthA);
+    return world()->toPixels(mPulleyJointDef.lengthA);
 }
 
 void Box2DPulleyJoint::setLengthA(float lengthA)
 {
-    if (mPulleyJointDef.lengthA == toMeters(lengthA))
+    if (mPulleyJointDef.lengthA == world()->toMeters(lengthA))
         return;
 
-    mPulleyJointDef.lengthA = toMeters(lengthA);
+    mPulleyJointDef.lengthA = world()->toMeters(lengthA);
     emit lengthAChanged();
 }
 
 float Box2DPulleyJoint::lengthB() const
 {
-    return toPixels(mPulleyJointDef.lengthB);
+    return world()->toPixels(mPulleyJointDef.lengthB);
 }
 
 void Box2DPulleyJoint::setLengthB(float lengthB)
 {
-    if (mPulleyJointDef.lengthB == toMeters(lengthB))
+    if (mPulleyJointDef.lengthB == world()->toMeters(lengthB))
         return;
 
-    mPulleyJointDef.lengthB = toMeters(lengthB);
+    mPulleyJointDef.lengthB = world()->toMeters(lengthB);
     emit lengthBChanged();
 }
 
@@ -72,49 +72,49 @@ void Box2DPulleyJoint::setRatio(float ratio)
 
 QPointF Box2DPulleyJoint::groundAnchorA() const
 {
-    return toPixels(mPulleyJointDef.groundAnchorA);
+    return world()->toPixels(mPulleyJointDef.groundAnchorA);
 }
 
 void Box2DPulleyJoint::setGroundAnchorA(const QPointF &groundAnchorA)
 {
-    mPulleyJointDef.groundAnchorA = toMeters(groundAnchorA);
+    mPulleyJointDef.groundAnchorA = world()->toMeters(groundAnchorA);
     emit groundAnchorAChanged();
 }
 
 QPointF Box2DPulleyJoint::groundAnchorB() const
 {
-    return toPixels(mPulleyJointDef.groundAnchorB);
+    return world()->toPixels(mPulleyJointDef.groundAnchorB);
 }
 
 void Box2DPulleyJoint::setGroundAnchorB(const QPointF &groundAnchorB)
 {
-    mPulleyJointDef.groundAnchorB = toMeters(groundAnchorB);
+    mPulleyJointDef.groundAnchorB = world()->toMeters(groundAnchorB);
     emit groundAnchorBChanged();
 }
 
 QPointF Box2DPulleyJoint::localAnchorA() const
 {
     if (pulleyJoint())
-        return toPixels(pulleyJoint()->GetAnchorA());
-    return toPixels(mPulleyJointDef.localAnchorA);
+        return world()->toPixels(pulleyJoint()->GetAnchorA());
+    return world()->toPixels(mPulleyJointDef.localAnchorA);
 }
 
 void Box2DPulleyJoint::setLocalAnchorA(const QPointF &localAnchorA)
 {
-    mPulleyJointDef.localAnchorA = toMeters(localAnchorA);
+    mPulleyJointDef.localAnchorA = world()->toMeters(localAnchorA);
     emit localAnchorAChanged();
 }
 
 QPointF Box2DPulleyJoint::localAnchorB() const
 {
     if (pulleyJoint())
-        return toPixels(pulleyJoint()->GetAnchorB());
-    return toPixels(mPulleyJointDef.localAnchorB);
+        return world()->toPixels(pulleyJoint()->GetAnchorB());
+    return world()->toPixels(mPulleyJointDef.localAnchorB);
 }
 
 void Box2DPulleyJoint::setLocalAnchorB(const QPointF &localAnchorB)
 {
-    mPulleyJointDef.localAnchorB = toMeters(localAnchorB);
+    mPulleyJointDef.localAnchorB = world()->toMeters(localAnchorB);
     emit localAnchorBChanged();
 }
 
@@ -125,20 +125,20 @@ b2Joint *Box2DPulleyJoint::createJoint()
         return 0;
     }
 
-    return world()->CreateJoint(&mPulleyJointDef);
+    return world()->world().CreateJoint(&mPulleyJointDef);
 }
 
 float Box2DPulleyJoint::getCurrentLengthA() const
 {
     if (pulleyJoint())
-        return toPixels(pulleyJoint()->GetCurrentLengthA());
+        return world()->toPixels(pulleyJoint()->GetCurrentLengthA());
     return lengthA();
 }
 
 float Box2DPulleyJoint::getCurrentLengthB() const
 {
     if (pulleyJoint())
-        return toPixels(pulleyJoint()->GetCurrentLengthB());
+        return world()->toPixels(pulleyJoint()->GetCurrentLengthB());
     return lengthB();
 }
 
diff --git a/box2drevolutejoint.cpp b/box2drevolutejoint.cpp
index 36f63c9c..7f843982 100644
--- a/box2drevolutejoint.cpp
+++ b/box2drevolutejoint.cpp
@@ -123,24 +123,24 @@ void Box2DRevoluteJoint::setEnableMotor(bool enableMotor)
 
 QPointF Box2DRevoluteJoint::localAnchorA() const
 {
-    return toPixels(mRevoluteJointDef.localAnchorA);
+    return world()->toPixels(mRevoluteJointDef.localAnchorA);
 }
 
 QPointF Box2DRevoluteJoint::localAnchorB() const
 {
-    return toPixels(mRevoluteJointDef.localAnchorB);
+    return world()->toPixels(mRevoluteJointDef.localAnchorB);
 }
 
 void Box2DRevoluteJoint::setLocalAnchorA(const QPointF &localAnchorA)
 {
-    mRevoluteJointDef.localAnchorA = toMeters(localAnchorA);
+    mRevoluteJointDef.localAnchorA = world()->toMeters(localAnchorA);
     mAnchorsAuto = false;
     emit localAnchorAChanged();
 }
 
 void Box2DRevoluteJoint::setLocalAnchorB(const QPointF &localAnchorB)
 {
-    mRevoluteJointDef.localAnchorB = toMeters(localAnchorB);
+    mRevoluteJointDef.localAnchorB = world()->toMeters(localAnchorB);
     mAnchorsAuto = false;
     emit localAnchorBChanged();
 }
@@ -153,7 +153,7 @@ b2Joint *Box2DRevoluteJoint::createJoint()
                                      mRevoluteJointDef.bodyA->GetWorldCenter());
     }
 
-    return world()->CreateJoint(&mRevoluteJointDef);
+    return world()->world().CreateJoint(&mRevoluteJointDef);
 }
 
 float Box2DRevoluteJoint::getJointAngle() const
diff --git a/box2dropejoint.cpp b/box2dropejoint.cpp
index b39c01e8..1489866d 100644
--- a/box2dropejoint.cpp
+++ b/box2dropejoint.cpp
@@ -36,12 +36,12 @@ Box2DRopeJoint::Box2DRopeJoint(QObject *parent) :
 
 float Box2DRopeJoint::maxLength() const
 {
-    return toPixels(mRopeJointDef.maxLength);
+    return world()->toPixels(mRopeJointDef.maxLength);
 }
 
 void Box2DRopeJoint::setMaxLength(float maxLength)
 {
-    const float maxLengthMeters = toMeters(maxLength);
+    const float maxLengthMeters = world()->toMeters(maxLength);
     if (mRopeJointDef.maxLength == maxLengthMeters)
         return;
 
@@ -53,29 +53,29 @@ void Box2DRopeJoint::setMaxLength(float maxLength)
 
 QPointF Box2DRopeJoint::localAnchorA() const
 {
-    return toPixels(mRopeJointDef.localAnchorA);
+    return world()->toPixels(mRopeJointDef.localAnchorA);
 }
 
 void Box2DRopeJoint::setLocalAnchorA(const QPointF &localAnchorA)
 {
-    mRopeJointDef.localAnchorA = toMeters(localAnchorA);
+    mRopeJointDef.localAnchorA = world()->toMeters(localAnchorA);
     emit localAnchorAChanged();
 }
 
 QPointF Box2DRopeJoint::localAnchorB() const
 {
-    return toPixels(mRopeJointDef.localAnchorB);
+    return world()->toPixels(mRopeJointDef.localAnchorB);
 }
 
 void Box2DRopeJoint::setLocalAnchorB(const QPointF &localAnchorB)
 {
-    mRopeJointDef.localAnchorB = toMeters(localAnchorB);
+    mRopeJointDef.localAnchorB = world()->toMeters(localAnchorB);
     emit localAnchorBChanged();
 }
 
 b2Joint *Box2DRopeJoint::createJoint()
 {
-    return world()->CreateJoint(&mRopeJointDef);
+    return world()->world().CreateJoint(&mRopeJointDef);
 }
 
 QPointF Box2DRopeJoint::getReactionForce(float32 inv_dt) const
diff --git a/box2dweldjoint.cpp b/box2dweldjoint.cpp
index 38c83ab3..960d455d 100644
--- a/box2dweldjoint.cpp
+++ b/box2dweldjoint.cpp
@@ -73,24 +73,24 @@ void Box2DWeldJoint::setDampingRatio(float dampingRatio)
 
 QPointF Box2DWeldJoint::localAnchorA() const
 {
-    return toPixels(mWeldJointDef.localAnchorA);
+    return world()->toPixels(mWeldJointDef.localAnchorA);
 }
 
 void Box2DWeldJoint::setLocalAnchorA(const QPointF &localAnchorA)
 {
-    mWeldJointDef.localAnchorA = toMeters(localAnchorA);
+    mWeldJointDef.localAnchorA = world()->toMeters(localAnchorA);
     mAnchorsAuto = false;
     emit localAnchorAChanged();
 }
 
 QPointF Box2DWeldJoint::localAnchorB() const
 {
-    return toPixels(mWeldJointDef.localAnchorB);
+    return world()->toPixels(mWeldJointDef.localAnchorB);
 }
 
 void Box2DWeldJoint::setLocalAnchorB(const QPointF &localAnchorB)
 {
-    mWeldJointDef.localAnchorB = toMeters(localAnchorB);
+    mWeldJointDef.localAnchorB = world()->toMeters(localAnchorB);
     mAnchorsAuto = false;
     emit localAnchorBChanged();
 }
@@ -103,5 +103,5 @@ b2Joint *Box2DWeldJoint::createJoint()
                                  mWeldJointDef.bodyA->GetWorldCenter());
     }
 
-    return world()->CreateJoint(&mWeldJointDef);
+    return world()->world().CreateJoint(&mWeldJointDef);
 }
diff --git a/box2dwheeljoint.cpp b/box2dwheeljoint.cpp
index ef5d708e..3c222aaa 100644
--- a/box2dwheeljoint.cpp
+++ b/box2dwheeljoint.cpp
@@ -98,36 +98,36 @@ void Box2DWheelJoint::setEnableMotor(bool enableMotor)
 
 QPointF Box2DWheelJoint::localAnchorA() const
 {
-    return toPixels(mWheelJointDef.localAnchorA);
+    return world()->toPixels(mWheelJointDef.localAnchorA);
 }
 
 void Box2DWheelJoint::setLocalAnchorA(const QPointF &localAnchorA)
 {
-    mWheelJointDef.localAnchorA = toMeters(localAnchorA);
+    mWheelJointDef.localAnchorA = world()->toMeters(localAnchorA);
     mAnchorsAuto = false;
     emit localAnchorAChanged();
 }
 
 QPointF Box2DWheelJoint::localAnchorB() const
 {
-    return toPixels(mWheelJointDef.localAnchorB);
+    return world()->toPixels(mWheelJointDef.localAnchorB);
 }
 
 void Box2DWheelJoint::setLocalAnchorB(const QPointF &localAnchorB)
 {
-    mWheelJointDef.localAnchorB = toMeters(localAnchorB);
+    mWheelJointDef.localAnchorB = world()->toMeters(localAnchorB);
     mAnchorsAuto = false;
     emit localAnchorBChanged();
 }
 
 QPointF Box2DWheelJoint::localAxisA() const
 {
-    return toPixels(mWheelJointDef.localAxisA);
+    return world()->toPixels(mWheelJointDef.localAxisA);
 }
 
 void Box2DWheelJoint::setLocalAxisA(const QPointF &localAxisA)
 {
-    mWheelJointDef.localAxisA = toMeters(localAxisA);
+    mWheelJointDef.localAxisA = world()->toMeters(localAxisA);
     mAnchorsAuto = false;
     emit localAxisAChanged();
 }
@@ -141,13 +141,13 @@ b2Joint *Box2DWheelJoint::createJoint()
                                   mWheelJointDef.localAxisA);
     }
 
-    return world()->CreateJoint(&mWheelJointDef);
+    return world()->world().CreateJoint(&mWheelJointDef);
 }
 
 float Box2DWheelJoint::getJointTranslation() const
 {
     if (wheelJoint())
-        return toPixels(wheelJoint()->GetJointTranslation());
+        return world()->toPixels(wheelJoint()->GetJointTranslation());
     return 0;
 }
 
diff --git a/box2dworld.cpp b/box2dworld.cpp
index ae00e707..b659413b 100644
--- a/box2dworld.cpp
+++ b/box2dworld.cpp
@@ -119,7 +119,6 @@ void ContactListener::PostSolve(b2Contact *contact, const b2ContactImpulse *impu
     emit mWorld->postSolve(&mContact);
 }
 
-
 Box2DWorld::Box2DWorld(QQuickItem *parent) :
     QQuickItem(parent),
     mWorld(b2Vec2(0.0f, -10.0f)),
@@ -129,7 +128,8 @@ Box2DWorld::Box2DWorld(QQuickItem *parent) :
     mPositionIterations(3),
     mIsRunning(true),
     mStepDriver(new StepDriver(this)),
-    mProfile(new Box2DProfile(&mWorld, this))
+    mProfile(new Box2DProfile(&mWorld, this)),
+    mPixelsPerMeter(32.0f)
 {
     mWorld.SetContactListener(mContactListener);
     mWorld.SetDestructionListener(this);
@@ -213,6 +213,19 @@ void Box2DWorld::setAutoClearForces(bool autoClearForces)
     emit autoClearForcesChanged();
 }
 
+void Box2DWorld::setPixelsPerMeter(float pixelsPerMeter)
+{
+    if (pixelsPerMeter <= 0.0f) {
+        qWarning("World: pixelsPerMeter must be > 0.0f");
+        return;
+    }
+
+    if (mPixelsPerMeter != pixelsPerMeter) {
+        mPixelsPerMeter = pixelsPerMeter;
+        pixelsPerMeterChanged();
+    }
+}
+
 void Box2DWorld::componentComplete()
 {
     QQuickItem::componentComplete();
@@ -286,7 +299,7 @@ void Box2DWorld::itemChange(ItemChange change, const ItemChangeData &value)
         if (change == ItemChildAddedChange) {
             QObject *child = value.item;
             if (Box2DBody *body = dynamic_cast<Box2DBody*>(child))
-                body->initialize(&mWorld);
+                body->initialize(this);
         }
     }
 
@@ -297,7 +310,7 @@ void Box2DWorld::initializeBodies(QQuickItem *parent)
 {
     foreach (QQuickItem *item, parent->childItems()) {
         if (Box2DBody *body = dynamic_cast<Box2DBody *>(item))
-            body->initialize(&mWorld);
+            body->initialize(this);
 
         initializeBodies(item);
     }
diff --git a/box2dworld.h b/box2dworld.h
index 5d1cd611..a03a1026 100644
--- a/box2dworld.h
+++ b/box2dworld.h
@@ -40,13 +40,6 @@ class Box2DWorld;
 class ContactListener;
 class StepDriver;
 
-// TODO: Maybe turn this into a property of the world, though it can't be
-// changed dynamically.
-static const float pixelsPerMeter = 32.0f; // 32 pixels in one meter
-static const float metersPerPixel = 1.0f / pixelsPerMeter;
-static const float pixelsPerMeterY = -pixelsPerMeter; // Y-axis inverted
-static const float metersPerPixelY = -metersPerPixel;
-
 /**
  * Small utility class to synchronize the stepping with the framerate.
  */
@@ -117,6 +110,7 @@ class Box2DWorld : public QQuickItem, b2DestructionListener
     Q_PROPERTY(QPointF gravity READ gravity WRITE setGravity NOTIFY gravityChanged)
     Q_PROPERTY(bool autoClearForces READ autoClearForces WRITE setAutoClearForces NOTIFY autoClearForcesChanged)
     Q_PROPERTY(Box2DProfile *profile READ profile NOTIFY stepped)
+    Q_PROPERTY(float pixelsPerMeter READ pixelsPerMeter WRITE setPixelsPerMeter NOTIFY pixelsPerMeterChanged)
 
 public:
     explicit Box2DWorld(QQuickItem *parent = 0);
@@ -142,6 +136,19 @@ class Box2DWorld : public QQuickItem, b2DestructionListener
 
     Box2DProfile *profile() const;
 
+    float pixelsPerMeter() const;
+    void setPixelsPerMeter(float pixelsPerMeter);
+
+    float metersPerPixel() const;
+    float pixelsPerMeterY() const;
+    float metersPerPixelY() const;
+
+    float toPixels(float length) const;
+    float toMeters(float length) const;
+
+    QPointF toPixels(const b2Vec2 &vec) const;
+    b2Vec2 toMeters(const QPointF &point) const;
+
     void componentComplete();
 
     b2World &world();
@@ -165,6 +172,7 @@ class Box2DWorld : public QQuickItem, b2DestructionListener
     void autoClearForcesChanged();
     void runningChanged();
     void stepped();
+    void pixelsPerMeterChanged();
 
 protected:
     void itemChange(ItemChange, const ItemChangeData &);
@@ -179,6 +187,7 @@ class Box2DWorld : public QQuickItem, b2DestructionListener
     bool mIsRunning;
     StepDriver *mStepDriver;
     Box2DProfile *mProfile;
+    float mPixelsPerMeter;
 };
 
 
@@ -265,65 +274,85 @@ inline Box2DProfile *Box2DWorld::profile() const
     return mProfile;
 }
 
-inline b2World &Box2DWorld::world()
+inline float Box2DWorld::pixelsPerMeter() const
 {
-    return mWorld;
+    return mPixelsPerMeter;
 }
 
-inline void Box2DWorld::clearForces()
+inline float Box2DWorld::metersPerPixel() const
 {
-    mWorld.ClearForces();
+    return 1.0f / pixelsPerMeter();
 }
 
+inline float Box2DWorld::pixelsPerMeterY() const
+{
+    return -pixelsPerMeter(); // Y-axis inverted
+}
+
+inline float Box2DWorld::metersPerPixelY() const
+{
+    return -metersPerPixel();
+}
 
 /**
- * Inverts the y-axis as required for forces and velocities.
+ * Converts lengths from Box2D to QML units.
  */
-inline QPointF invertY(const b2Vec2 &vec)
+inline float Box2DWorld::toPixels(float length) const
 {
-    return QPointF(vec.x, -vec.y);
+    return length * pixelsPerMeter();
 }
 
 /**
- * Inverts the y-axis as required for forces and velocities.
+ * Converts lengths from QML to Box2D units.
  */
-inline b2Vec2 invertY(const QPointF &vec)
+inline float Box2DWorld::toMeters(float length) const
 {
-    return b2Vec2(vec.x(), -vec.y());
+    return length * metersPerPixel();
 }
 
 /**
- * Converts lengths from Box2D to QML units.
+ * Converts positions and sizes from Box2D to QML coordinates.
  */
-inline float toPixels(float length)
+inline QPointF Box2DWorld::toPixels(const b2Vec2 &vec) const
 {
-    return length * pixelsPerMeter;
+    return QPointF(vec.x * pixelsPerMeter(),
+                   vec.y * pixelsPerMeterY());
 }
 
 /**
- * Converts lengths from QML to Box2D units.
+ * Converts positions and sizes from QML to Box2D coordinates.
  */
-inline float toMeters(float length)
+inline b2Vec2 Box2DWorld::toMeters(const QPointF &point) const
+{
+    return b2Vec2(point.x() * metersPerPixel(),
+                  point.y() * metersPerPixelY());
+}
+
+inline b2World &Box2DWorld::world()
+{
+    return mWorld;
+}
+
+inline void Box2DWorld::clearForces()
 {
-    return length * metersPerPixel;
+    mWorld.ClearForces();
 }
 
+
 /**
- * Converts positions and sizes from Box2D to QML coordinates.
+ * Inverts the y-axis as required for forces and velocities.
  */
-inline QPointF toPixels(const b2Vec2 &vec)
+inline QPointF invertY(const b2Vec2 &vec)
 {
-    return QPointF(vec.x * pixelsPerMeter,
-                   vec.y * pixelsPerMeterY);
+    return QPointF(vec.x, -vec.y);
 }
 
 /**
- * Converts positions and sizes from QML to Box2D coordinates.
+ * Inverts the y-axis as required for forces and velocities.
  */
-inline b2Vec2 toMeters(const QPointF &point)
+inline b2Vec2 invertY(const QPointF &vec)
 {
-    return b2Vec2(point.x() * metersPerPixel,
-                  point.y() * metersPerPixelY);
+    return b2Vec2(vec.x(), -vec.y());
 }
 
 /**