Merge pull request #1598 from AndrewMeadows/paddle-fixes-2

Paddle fixes 2

interface/src/ParticleTreeRenderer.cpp

@@ -32,7 +32,7 @@ void ParticleTreeRenderer::renderElement(OctreeElement* element, RenderArgs* arg
     // we need to iterate the actual particles of the element
     ParticleTreeElement* particleTreeElement = (ParticleTreeElement*)element;
     
-    const std::vector<Particle>& particles = particleTreeElement->getParticles();
+    const QList<Particle>& particles = particleTreeElement->getParticles();
     
     uint16_t numberOfParticles = particles.size();
     

libraries/particles/src/Particle.cpp

@@ -474,21 +474,21 @@ void Particle::adjustEditPacketForClockSkew(unsigned char* codeColorBuffer, ssiz
     }
 }
 
+// MIN_VALID_SPEED is obtained by computing speed gained at one gravity during the shortest expected frame period
+const float MIN_EXPECTED_FRAME_PERIOD = 0.005f;  // 1/200th of a second
+const float MIN_VALID_SPEED = 9.8 * MIN_EXPECTED_FRAME_PERIOD / (float)(TREE_SCALE); 
 
-void Particle::update() {
+void Particle::update(const uint64_t& now) {
-    uint64_t now = usecTimestampNow();
+    float timeElapsed = (float)(now - _lastUpdated) / (float)(USECS_PER_SECOND);
-    float elapsed = static_cast<float>(now - _lastUpdated);
     _lastUpdated = now;
-    float timeElapsed = elapsed / static_cast<float>(USECS_PER_SECOND);
 
     // calculate our default shouldDie state... then allow script to change it if it wants...
-    float velocityScalar = glm::length(getVelocity());
+    float speed = glm::length(_velocity);
-    const float STILL_MOVING = 0.05f / static_cast<float>(TREE_SCALE);
+    bool isStopped = (speed < MIN_VALID_SPEED);
-    bool isStillMoving = (velocityScalar > STILL_MOVING);
+    const uint64_t REALLY_OLD = 30 * USECS_PER_SECOND; // 30 seconds
-    const float REALLY_OLD = 30.0f; // 30 seconds
+    bool isReallyOld = ((now - _created) > REALLY_OLD);
-    bool isReallyOld = (getLifetime() > REALLY_OLD);
     bool isInHand = getInHand();
-    bool shouldDie = getShouldDie() || (!isInHand && !isStillMoving && isReallyOld);
+    bool shouldDie = getShouldDie() || (!isInHand && isStopped && isReallyOld);
     setShouldDie(shouldDie);
 
     runUpdateScript(); // allow the javascript to alter our state

libraries/particles/src/Particle.h

@@ -117,7 +117,7 @@ public:
 
     static void adjustEditPacketForClockSkew(unsigned char* codeColorBuffer, ssize_t length, int clockSkew);
 
-    void update();
+    void update(const uint64_t& now);
     void collisionWithParticle(Particle* other);
     void collisionWithVoxel(VoxelDetail* voxel);
 

libraries/particles/src/ParticleCollisionSystem.cpp

@@ -11,7 +11,6 @@
 #include <AbstractAudioInterface.h>
 #include <VoxelTree.h>
 #include <AvatarData.h>
-#include <CollisionInfo.h>
 #include <HeadData.h>
 #include <HandData.h>
 
@@ -43,7 +42,7 @@ bool ParticleCollisionSystem::updateOperation(OctreeElement* element, void* extr
     ParticleTreeElement* particleTreeElement = static_cast<ParticleTreeElement*>(element);
 
     // iterate the particles...
-    std::vector<Particle>& particles = particleTreeElement->getParticles();
+    QList<Particle>& particles = particleTreeElement->getParticles();
     uint16_t numberOfParticles = particles.size();
     for (uint16_t i = 0; i < numberOfParticles; i++) {
         Particle* particle = &particles[i];
@@ -72,18 +71,18 @@ void ParticleCollisionSystem::updateCollisionWithVoxels(Particle* particle) {
     glm::vec3 center = particle->getPosition() * (float)(TREE_SCALE);
     float radius = particle->getRadius() * (float)(TREE_SCALE);
     const float ELASTICITY = 0.4f;
-    const float DAMPING = 0.0f;
+    const float DAMPING = 0.05f;
     const float COLLISION_FREQUENCY = 0.5f;
-    glm::vec3 penetration;
+    CollisionInfo collisionInfo;
     VoxelDetail* voxelDetails = NULL;
-    if (_voxels->findSpherePenetration(center, radius, penetration, (void**)&voxelDetails)) {
+    if (_voxels->findSpherePenetration(center, radius, collisionInfo._penetration, (void**)&voxelDetails)) {
 
         // let the particles run their collision scripts if they have them
         particle->collisionWithVoxel(voxelDetails);
 
-        penetration /= (float)(TREE_SCALE);
+        collisionInfo._penetration /= (float)(TREE_SCALE);
-        updateCollisionSound(particle, penetration, COLLISION_FREQUENCY);
+        updateCollisionSound(particle, collisionInfo._penetration, COLLISION_FREQUENCY);
-        applyHardCollision(particle, penetration, ELASTICITY, DAMPING);
+        applyHardCollision(particle, ELASTICITY, DAMPING, collisionInfo);
 
         delete voxelDetails; // cleanup returned details
     }
@@ -136,6 +135,10 @@ void ParticleCollisionSystem::updateCollisionWithParticles(Particle* particleA)
     }
 }
 
+// MIN_VALID_SPEED is obtained by computing speed gained at one gravity after the shortest expected frame
+const float MIN_EXPECTED_FRAME_PERIOD = 0.0167f;  // 1/60th of a second
+const float HALTING_SPEED = 9.8 * MIN_EXPECTED_FRAME_PERIOD / (float)(TREE_SCALE); 
+
 void ParticleCollisionSystem::updateCollisionWithAvatars(Particle* particle) {
 
     // particles that are in hand, don't collide with avatars
@@ -146,18 +149,18 @@ void ParticleCollisionSystem::updateCollisionWithAvatars(Particle* particle) {
     glm::vec3 center = particle->getPosition() * (float)(TREE_SCALE);
     float radius = particle->getRadius() * (float)(TREE_SCALE);
     const float ELASTICITY = 0.9f;
-    const float DAMPING = 0.0f;
+    const float DAMPING = 0.1f;
     const float COLLISION_FREQUENCY = 0.5f;
     glm::vec3 penetration;
 
     // first check the selfAvatar if set...
     if (_selfAvatar) {
         AvatarData* avatar = (AvatarData*)_selfAvatar;
-        CollisionInfo collision;
+        CollisionInfo collisionInfo;
-        if (avatar->findSphereCollision(center, radius, collision)) {
+        if (avatar->findSphereCollision(center, radius, collisionInfo)) {
-            collision._addedVelocity /= (float)(TREE_SCALE);
+            collisionInfo._addedVelocity /= (float)(TREE_SCALE);
-            glm::vec3 relativeVelocity = collision._addedVelocity - particle->getVelocity();
+            glm::vec3 relativeVelocity = collisionInfo._addedVelocity - particle->getVelocity();
-            if (glm::dot(relativeVelocity, collision._penetration) < 0.f) {
+            if (glm::dot(relativeVelocity, collisionInfo._penetration) < 0.f) {
                 // only collide when particle and collision point are moving toward each other
                 // (doing this prevents some "collision snagging" when particle penetrates the object)
 
@@ -165,17 +168,20 @@ void ParticleCollisionSystem::updateCollisionWithAvatars(Particle* particle) {
                 // NOTE: the physics are wrong (particles cannot roll) but it IS possible to catch a slow moving particle.
                 // TODO: make this less hacky when we have more per-collision details
                 float elasticity = ELASTICITY;
-                float SLOW_PADDLE_SPEED = 5.0e-5f;
+                float attenuationFactor = glm::length(collisionInfo._addedVelocity) / HALTING_SPEED;
-                float attenuationFactor = glm::length(collision._addedVelocity) / SLOW_PADDLE_SPEED;
+                float damping = DAMPING;
                 if (attenuationFactor < 1.f) {
-                    collision._addedVelocity *= attenuationFactor;
+                    collisionInfo._addedVelocity *= attenuationFactor;
                     elasticity *= attenuationFactor;
+                    // NOTE: the math below keeps the damping piecewise continuous, 
+                    // while ramping it up to 1.0 when attenuationFactor = 0
+                    damping = DAMPING + (1.f - attenuationFactor) * (1.f - DAMPING);
                 }
                 // HACK END
 
-                collision._penetration /= (float)(TREE_SCALE);
+                collisionInfo._penetration /= (float)(TREE_SCALE);
-                updateCollisionSound(particle, collision._penetration, COLLISION_FREQUENCY);
+                updateCollisionSound(particle, collisionInfo._penetration, COLLISION_FREQUENCY);
-                applyHardCollision(particle, collision._penetration, elasticity, DAMPING, collision._addedVelocity);
+                applyHardCollision(particle, elasticity, damping, collisionInfo);
             }
         }
     }
@@ -185,36 +191,37 @@ void ParticleCollisionSystem::updateCollisionWithAvatars(Particle* particle) {
         //qDebug() << "updateCollisionWithAvatars()... node:" << *node << "\n";
         if (node->getLinkedData() && node->getType() == NODE_TYPE_AGENT) {
             AvatarData* avatar = static_cast<AvatarData*>(node->getLinkedData());
-            CollisionInfo collision;
+            CollisionInfo collisionInfo;
-            if (avatar->findSphereCollision(center, radius, collision)) {
+            if (avatar->findSphereCollision(center, radius, collisionInfo)) {
-                collision._addedVelocity /= (float)(TREE_SCALE);
+                collisionInfo._addedVelocity /= (float)(TREE_SCALE);
-                glm::vec3 relativeVelocity = collision._addedVelocity - particle->getVelocity();
+                glm::vec3 relativeVelocity = collisionInfo._addedVelocity - particle->getVelocity();
-                if (glm::dot(relativeVelocity, collision._penetration) < 0.f) {
+                if (glm::dot(relativeVelocity, collisionInfo._penetration) < 0.f) {
                     // HACK BEGIN: to allow paddle hands to "hold" particles we attenuate soft collisions against the avatar.  
                     // NOTE: the physics are wrong (particles cannot roll) but it IS possible to catch a slow moving particle.
                     // TODO: make this less hacky when we have more per-collision details
                     float elasticity = ELASTICITY;
-                    float SLOW_PADDLE_SPEED = 5.0e-5f;
+                    float attenuationFactor = glm::length(collisionInfo._addedVelocity) / HALTING_SPEED;
-                    float attenuationFactor = glm::length(collision._addedVelocity) / SLOW_PADDLE_SPEED;
+                    float damping = DAMPING;
                     if (attenuationFactor < 1.f) {
-                        collision._addedVelocity *= attenuationFactor;
+                        collisionInfo._addedVelocity *= attenuationFactor;
                         elasticity *= attenuationFactor;
+                        // NOTE: the math below keeps the damping piecewise continuous, 
+                        // while ramping it up to 1.0 when attenuationFactor = 0
+                        damping = DAMPING + (1.f - attenuationFactor) * (1.f - DAMPING);
                     }
                     // HACK END
 
-                    collision._penetration /= (float)(TREE_SCALE);
+                    collisionInfo._penetration /= (float)(TREE_SCALE);
-                    updateCollisionSound(particle, collision._penetration, COLLISION_FREQUENCY);
+                    updateCollisionSound(particle, collisionInfo._penetration, COLLISION_FREQUENCY);
-                    applyHardCollision(particle, collision._penetration, ELASTICITY, DAMPING, collision._addedVelocity);    
+                    applyHardCollision(particle, ELASTICITY, damping, collisionInfo);    
                 }
             }
         }
     }
 }
 
-
 // TODO: convert applyHardCollision() to take a CollisionInfo& instead of penetration + addedVelocity
-void ParticleCollisionSystem::applyHardCollision(Particle* particle, const glm::vec3& penetration,
+void ParticleCollisionSystem::applyHardCollision(Particle* particle, float elasticity, float damping, const CollisionInfo& collisionInfo) {
-                                                 float elasticity, float damping, const glm::vec3& addedVelocity) {
     //
     //  Update the particle in response to a hard collision.  Position will be reset exactly
     //  to outside the colliding surface.  Velocity will be modified according to elasticity.
@@ -226,20 +233,19 @@ void ParticleCollisionSystem::applyHardCollision(Particle* particle, const glm::
     glm::vec3 velocity = particle->getVelocity();
 
     const float EPSILON = 0.0f;
-    float velocityDotPenetration = glm::dot(velocity, penetration);
+    glm::vec3 relativeVelocity = collisionInfo._addedVelocity - velocity;
-    if (velocityDotPenetration > EPSILON) {
+    float velocityDotPenetration = glm::dot(relativeVelocity, collisionInfo._penetration);
-        position -= penetration;
+    if (velocityDotPenetration < EPSILON) {
-        static float HALTING_VELOCITY = 0.2f / (float)(TREE_SCALE);
+        // particle is moving into collision surface
-        // cancel out the velocity component in the direction of penetration
+        position -= collisionInfo._penetration;
 
-        float penetrationLength = glm::length(penetration);
+        if (glm::length(relativeVelocity) < HALTING_SPEED) {
-        glm::vec3 direction = penetration / penetrationLength;
+            // static friction kicks in and particle moves with colliding object
-        velocity -= (glm::dot(velocity, direction) * (1.0f + elasticity)) * direction;
+            velocity = collisionInfo._addedVelocity;
-        velocity += addedVelocity;
+        } else {
-        velocity *= glm::clamp(1.f - damping, 0.0f, 1.0f);
+            glm::vec3 direction = glm::normalize(collisionInfo._penetration);
-        if (glm::length(velocity) < HALTING_VELOCITY) {
+            velocity += glm::dot(relativeVelocity, direction) * (1.0f + elasticity) * direction;    // dynamic reflection
-            // If moving really slowly after a collision, and not applying forces, stop altogether
+            velocity += glm::clamp(damping, 0.0f, 1.0f) * (relativeVelocity - glm::dot(relativeVelocity, direction) * direction);   // dynamic friction
-            velocity *= 0.f;
         }
     }
     const bool wantDebug = false;

libraries/particles/src/ParticleCollisionSystem.h

@@ -16,6 +16,7 @@
 #include <QtScript/QScriptEngine>
 #include <QtCore/QObject>
 
+#include <CollisionInfo.h>
 #include <SharedUtil.h>
 #include <OctreePacketData.h>
 
@@ -46,8 +47,7 @@ public:
     void updateCollisionWithVoxels(Particle* particle);
     void updateCollisionWithParticles(Particle* particle);
     void updateCollisionWithAvatars(Particle* particle);
-    void applyHardCollision(Particle* particle, const glm::vec3& penetration, float elasticity, float damping, 
+    void applyHardCollision(Particle* particle, float elasticity, float damping, const CollisionInfo& collisionInfo);
-                            const glm::vec3& addedVelocity = NO_ADDED_VELOCITY);
     void updateCollisionSound(Particle* particle, const glm::vec3 &penetration, float frequency);
 
 private:

libraries/particles/src/ParticleTreeElement.cpp

@@ -11,12 +11,14 @@
 #include "ParticleTree.h"
 #include "ParticleTreeElement.h"
 
-ParticleTreeElement::ParticleTreeElement(unsigned char* octalCode) : OctreeElement() { 
+ParticleTreeElement::ParticleTreeElement(unsigned char* octalCode) : OctreeElement(), _particles(NULL) { 
     init(octalCode);
 };
 
 ParticleTreeElement::~ParticleTreeElement() {
     _voxelMemoryUsage -= sizeof(ParticleTreeElement);
+    delete _particles;
+    _particles = NULL;
 }
 
 // This will be called primarily on addChildAt(), which means we're adding a child of our
@@ -31,6 +33,7 @@ OctreeElement* ParticleTreeElement::createNewElement(unsigned char* octalCode) c
 
 void ParticleTreeElement::init(unsigned char* octalCode) {
     OctreeElement::init(octalCode);
+    _particles = new QList<Particle>;
     _voxelMemoryUsage += sizeof(ParticleTreeElement);
 }
 
@@ -45,12 +48,12 @@ bool ParticleTreeElement::appendElementData(OctreePacketData* packetData) const
     bool success = true; // assume the best...
 
     // write our particles out...
-    uint16_t numberOfParticles = _particles.size();
+    uint16_t numberOfParticles = _particles->size();
     success = packetData->appendValue(numberOfParticles);
 
     if (success) {
         for (uint16_t i = 0; i < numberOfParticles; i++) {
-            const Particle& particle = _particles[i];
+            const Particle& particle = (*_particles)[i];
             success = particle.appendParticleData(packetData);
             if (!success) {
                 break;
@@ -62,35 +65,42 @@ bool ParticleTreeElement::appendElementData(OctreePacketData* packetData) const
 
 void ParticleTreeElement::update(ParticleTreeUpdateArgs& args) {
     markWithChangedTime();
+    // TODO: early exit when _particles is empty
 
     // update our contained particles
-    uint16_t numberOfParticles = _particles.size();
+    QList<Particle>::iterator particleItr = _particles->begin();
-
+    while(particleItr != _particles->end()) {
-    for (uint16_t i = 0; i < numberOfParticles; i++) {
+        Particle& particle = (*particleItr);
-        _particles[i].update();
+        particle.update(_lastChanged);
 
         // If the particle wants to die, or if it's left our bounding box, then move it
         // into the arguments moving particles. These will be added back or deleted completely
-        if (_particles[i].getShouldDie() || !_box.contains(_particles[i].getPosition())) {
+        if (particle.getShouldDie() || !_box.contains(particle.getPosition())) {
-            args._movingParticles.push_back(_particles[i]);
+            args._movingParticles.push_back(particle);
             
             // erase this particle
-            _particles.erase(_particles.begin()+i);
+            particleItr = _particles->erase(particleItr);
-            
+        }
-            // reduce our index since we just removed this item
+        else
-            i--;
+        {
-            numberOfParticles--;
+            ++particleItr;
         }
     }
+    // TODO: if _particles is empty after while loop consider freeing memory in _particles if
+    // internal array is too big (QList internal array does not decrease size except in dtor and
+    // assignment operator).  Otherwise _particles could become a "resource leak" for large
+    // roaming piles of particles.
 }
 
 bool ParticleTreeElement::findSpherePenetration(const glm::vec3& center, float radius, 
                                     glm::vec3& penetration, void** penetratedObject) const {
                                     
-    uint16_t numberOfParticles = _particles.size();
+    QList<Particle>::iterator particleItr = _particles->begin();
-    for (uint16_t i = 0; i < numberOfParticles; i++) {
+    QList<Particle>::const_iterator particleEnd = _particles->end();
-        glm::vec3 particleCenter = _particles[i].getPosition();
+    while(particleItr != particleEnd) {
-        float particleRadius = _particles[i].getRadius();
+        Particle& particle = (*particleItr);
+        glm::vec3 particleCenter = particle.getPosition();
+        float particleRadius = particle.getRadius();
         
         // don't penetrate yourself
         if (particleCenter == center && particleRadius == radius) {
@@ -102,23 +112,28 @@ bool ParticleTreeElement::findSpherePenetration(const glm::vec3& center, float r
         const bool IN_HAND_PARTICLES_DONT_COLLIDE = false;
         if (IN_HAND_PARTICLES_DONT_COLLIDE) {
             // don't penetrate if the particle is "inHand" -- they don't collide
-            if (_particles[i].getInHand()) {
+            if (particle.getInHand()) {
-                return false;
+                ++particleItr;
+                continue;
             }
         }
         
         if (findSphereSpherePenetration(center, radius, particleCenter, particleRadius, penetration)) {
-            *penetratedObject = (void*)&_particles[i];
+            // return true on first valid particle penetration
+            *penetratedObject = (void*)(&particle);
             return true;
         }
+        ++particleItr;
     }
     return false;
 }
 
 bool ParticleTreeElement::containsParticle(const Particle& particle) const {
-    uint16_t numberOfParticles = _particles.size();
+    // TODO: remove this method and force callers to use getParticleWithID() instead
+    uint16_t numberOfParticles = _particles->size();
+    uint32_t particleID = particle.getID();
     for (uint16_t i = 0; i < numberOfParticles; i++) {
-        if (_particles[i].getID() == particle.getID()) {
+        if ((*_particles)[i].getID() == particleID) {
             return true;
         }
     }
@@ -126,13 +141,17 @@ bool ParticleTreeElement::containsParticle(const Particle& particle) const {
 }
 
 bool ParticleTreeElement::updateParticle(const Particle& particle) {
+    // NOTE: this method must first lookup the particle by ID, hence it is O(N) 
+    // and "particle is not found" is worst-case (full N) but maybe we don't care? 
+    // (guaranteed that num particles per elemen is small?)
     const bool wantDebug = false;
-    uint16_t numberOfParticles = _particles.size();
+    uint16_t numberOfParticles = _particles->size();
     for (uint16_t i = 0; i < numberOfParticles; i++) {
-        if (_particles[i].getID() == particle.getID()) {
+        Particle& thisParticle = (*_particles)[i];
-            int difference = _particles[i].getLastUpdated() - particle.getLastUpdated();
+        if (thisParticle.getID() == particle.getID()) {
-            bool changedOnServer = _particles[i].getLastEdited() < particle.getLastEdited();
+            int difference = thisParticle.getLastUpdated() - particle.getLastUpdated();
-            bool localOlder = _particles[i].getLastUpdated() < particle.getLastUpdated();
+            bool changedOnServer = thisParticle.getLastEdited() < particle.getLastEdited();
+            bool localOlder = thisParticle.getLastUpdated() < particle.getLastUpdated();
             if (changedOnServer || localOlder) {                
                 if (wantDebug) {
                     printf("local particle [id:%d] %s and %s than server particle by %d, particle.isNewlyCreated()=%s\n", 
@@ -140,7 +159,7 @@ bool ParticleTreeElement::updateParticle(const Particle& particle) {
                             (localOlder ? "OLDER" : "NEWER"),               
                             difference, debug::valueOf(particle.isNewlyCreated()) );
                 }
-                _particles[i].copyChangedProperties(particle);
+                thisParticle.copyChangedProperties(particle);
             } else {
                 if (wantDebug) {
                     printf(">>> IGNORING SERVER!!! Would've caused jutter! <<<  "
@@ -159,22 +178,23 @@ bool ParticleTreeElement::updateParticle(const Particle& particle) {
 const Particle* ParticleTreeElement::getClosestParticle(glm::vec3 position) const {
     const Particle* closestParticle = NULL;
     float closestParticleDistance = FLT_MAX;
-    uint16_t numberOfParticles = _particles.size();
+    uint16_t numberOfParticles = _particles->size();
     for (uint16_t i = 0; i < numberOfParticles; i++) {
-        float distanceToParticle = glm::distance(position, _particles[i].getPosition());
+        float distanceToParticle = glm::distance(position, (*_particles)[i].getPosition());
         if (distanceToParticle < closestParticleDistance) {
-            closestParticle = &_particles[i];
+            closestParticle = &(*_particles)[i];
         }
     }
     return closestParticle;    
 }
 
 const Particle* ParticleTreeElement::getParticleWithID(uint32_t id) const {
+    // NOTE: this lookup is O(N) but maybe we don't care? (guaranteed that num particles per elemen is small?)
     const Particle* foundParticle = NULL;
-    uint16_t numberOfParticles = _particles.size();
+    uint16_t numberOfParticles = _particles->size();
     for (uint16_t i = 0; i < numberOfParticles; i++) {
-        if (_particles[i].getID() == id) {
+        if ((*_particles)[i].getID() == id) {
-            foundParticle = &_particles[i];
+            foundParticle = &(*_particles)[i];
             break;
         }
     }
@@ -229,7 +249,7 @@ bool ParticleTreeElement::collapseChildren() {
 
 
 void ParticleTreeElement::storeParticle(const Particle& particle, Node* senderNode) {
-    _particles.push_back(particle);
+    _particles->push_back(particle);
     markWithChangedTime();
 }
 

libraries/particles/src/ParticleTreeElement.h

@@ -10,9 +10,10 @@
 #ifndef __hifi__ParticleTreeElement__
 #define __hifi__ParticleTreeElement__
 
-#include <vector>
+//#include <vector>
 
 #include <OctreeElement.h>
+#include <QList>
 
 #include "Particle.h"
 #include "ParticleTree.h"
@@ -22,7 +23,7 @@ class ParticleTreeElement;
 
 class ParticleTreeUpdateArgs {
 public:
-    std::vector<Particle> _movingParticles;
+    QList<Particle> _movingParticles;
 };
 
 class ParticleTreeElement : public OctreeElement {
@@ -34,7 +35,6 @@ class ParticleTreeElement : public OctreeElement {
     
 public:
     virtual ~ParticleTreeElement();
-    virtual void init(unsigned char * octalCode);
 
     // type safe versions of OctreeElement methods
     ParticleTreeElement* getChildAtIndex(int index) { return (ParticleTreeElement*)OctreeElement::getChildAtIndex(index); }
@@ -79,9 +79,9 @@ public:
     virtual bool findSpherePenetration(const glm::vec3& center, float radius, 
                         glm::vec3& penetration, void** penetratedObject) const;
 
-    const std::vector<Particle>& getParticles() const { return _particles; }
+    const QList<Particle>& getParticles() const { return *_particles; }
-    std::vector<Particle>& getParticles() { return _particles; }
+    QList<Particle>& getParticles() { return *_particles; }
-    bool hasParticles() const { return _particles.size() > 0; }
+    bool hasParticles() const { return _particles->size() > 0; }
     
     void update(ParticleTreeUpdateArgs& args);
     void setTree(ParticleTree* tree) { _myTree = tree; }
@@ -93,10 +93,12 @@ public:
     
 
 protected:
+    virtual void init(unsigned char * octalCode);
+
     void storeParticle(const Particle& particle, Node* senderNode = NULL);
 
     ParticleTree* _myTree;
-    std::vector<Particle> _particles;
+    QList<Particle>* _particles;
 };
 
 #endif /* defined(__hifi__ParticleTreeElement__) */