diff --git a/interface/src/renderer/Model.cpp b/interface/src/renderer/Model.cpp
index 03c1544aab..3003e29f54 100644
--- a/interface/src/renderer/Model.cpp
+++ b/interface/src/renderer/Model.cpp
@@ -37,6 +37,7 @@ Model::Model(QObject* parent) :
     _scaleToFit(false),
     _scaleToFitLargestDimension(0.0f),
     _scaledToFit(false),
+    _simulationIndex(-1),
     _snapModelToCenter(false),
     _snappedToCenter(false),
     _rootIndex(-1),
@@ -774,6 +775,34 @@ AnimationHandlePointer Model::createAnimationHandle() {
     return handle;
 }
 
+quint8 BITS_FOR_SHAPE_INDEX = 15;
+int MAX_SIMULATION_ID = 1 << (31 - BITS_FOR_SHAPE_INDEX);
+
+void Model::setSimulationIndex(int index) {
+    _simulationIndex = index;
+
+    if (_simulationIndex < 0 || _simulationIndex > MAX_SIMULATION_ID) {
+        // clear simulation ID's of all the shapes
+        for (int i = 0; i < _jointShapes.size(); i++) {
+            Shape* shape = _jointShapes[i];
+            if (shape) {
+                shape->setSimulationID(-1);
+            }
+        }
+    } else {
+        // update the simulation ID's of the shapes
+        // upper bits store this Model's index...
+        int shiftedIndex = _simulationIndex << BITS_FOR_SHAPE_INDEX;
+        for (int i = 0; i < _jointShapes.size(); i++) {
+            Shape* shape = _jointShapes[i];
+            if (shape) {
+                // ... lower bits are for the shape's index
+                shape->setSimulationID(shiftedIndex + i);
+            }
+        }
+    }
+}
+
 void Model::clearShapes() {
     for (int i = 0; i < _jointShapes.size(); ++i) {
         delete _jointShapes[i];
diff --git a/interface/src/renderer/Model.h b/interface/src/renderer/Model.h
index f8d4cf628b..aa0b34d750 100644
--- a/interface/src/renderer/Model.h
+++ b/interface/src/renderer/Model.h
@@ -134,9 +134,10 @@ public:
     QStringList getJointNames() const;
     
     AnimationHandlePointer createAnimationHandle();
-    
+
     const QList<AnimationHandlePointer>& getRunningAnimations() const { return _runningAnimations; }
-    
+   
+    void setSimulationIndex(int index);
     void clearShapes();
     void rebuildShapes();
     void resetShapePositions(); // DEBUG method
@@ -177,6 +178,8 @@ protected:
     bool _scaleToFit; /// If you set scaleToFit, we will calculate scale based on MeshExtents
     float _scaleToFitLargestDimension; /// this is the dimension that scale to fit will use
     bool _scaledToFit; /// have we scaled to fit
+
+    int _simulationIndex;   // set by SimulationEngine (if any)
     
     bool _snapModelToCenter; /// is the model's offset automatically adjusted to center around 0,0,0 in model space
     bool _snappedToCenter; /// are we currently snapped to center
diff --git a/libraries/shared/src/CollisionInfo.cpp b/libraries/shared/src/CollisionInfo.cpp
index 32deb56cd1..a1c3f0b368 100644
--- a/libraries/shared/src/CollisionInfo.cpp
+++ b/libraries/shared/src/CollisionInfo.cpp
@@ -47,6 +47,8 @@ void CollisionList::clear() {
         //collision._intData = 0;
         //collision._floatDAta = 0.0f;
         //collision._vecData = glm::vec3(0.0f);
+        //collision._shapeA = -1;
+        //collision._shapeB = -1;
         //collision._damping;
         //collision._elasticity;
         //collision._contactPoint;
diff --git a/libraries/shared/src/CollisionInfo.h b/libraries/shared/src/CollisionInfo.h
index cf48701a2b..ff228e3863 100644
--- a/libraries/shared/src/CollisionInfo.h
+++ b/libraries/shared/src/CollisionInfo.h
@@ -33,6 +33,8 @@ public:
     CollisionInfo() 
         : _data(NULL),
         _intData(0),
+        _shapeA(-1),
+        _shapeB(-1),
         _damping(0.f),
         _elasticity(1.f),
         _contactPoint(0.f), 
@@ -43,6 +45,8 @@ public:
     CollisionInfo(qint32 type)
         : _data(NULL),
         _intData(0),
+        _shapeA(-1),
+        _shapeB(-1),
         _damping(0.f),
         _elasticity(1.f),
         _contactPoint(0.f), 
@@ -58,6 +62,9 @@ public:
     float _floatData;
     glm::vec3 _vecData;
 
+    int _shapeA;  // ID of shapeA in its SimulationEngine
+    int _shapeB;  // ID of shapeB in its SimulationEngine
+
     float _damping;           // range [0,1] of friction coeficient
     float _elasticity;        // range [0,1] of energy conservation
     glm::vec3 _contactPoint;  // world-frame point on BodyA that is deepest into BodyB
diff --git a/libraries/shared/src/Shape.h b/libraries/shared/src/Shape.h
index 87b84ea73b..a9bddc00df 100644
--- a/libraries/shared/src/Shape.h
+++ b/libraries/shared/src/Shape.h
@@ -23,11 +23,10 @@ public:
         SPHERE_SHAPE,
         CAPSULE_SHAPE,
         PLANE_SHAPE,
-        BOX_SHAPE,
         LIST_SHAPE
     };
 
-    Shape() : _type(UNKNOWN_SHAPE), _boundingRadius(0.f), _position(0.f), _rotation() { }
+    Shape() : _type(UNKNOWN_SHAPE), _simulationID(-1), _boundingRadius(0.f), _position(0.f), _rotation() { }
     virtual ~Shape() {}
 
     int getType() const { return _type; }
@@ -38,6 +37,9 @@ public:
     virtual void setPosition(const glm::vec3& position) { _position = position; }
     virtual void setRotation(const glm::quat& rotation) { _rotation = rotation; }
 
+    void setSimulationID(int id) { _simulationID = id; }
+    int getSimulationID() const { return _simulationID; }
+
 protected:
     // these ctors are protected (used by derived classes only)
     Shape(Type type) : _type(type), _boundingRadius(0.f), _position(0.f), _rotation() {}
@@ -51,6 +53,7 @@ protected:
     void setBoundingRadius(float radius) { _boundingRadius = radius; }
 
     int _type;
+    int _simulationID;    // shape's simulation ID in SimulationEngine
     float _boundingRadius;
     glm::vec3 _position;
     glm::quat _rotation;