Moving applyHardCollision to the Particle class. Adding daming and elasticity to CollisionInfo.

libraries/particles/src/Particle.cpp

@@ -668,7 +668,50 @@ void Particle::adjustEditPacketForClockSkew(unsigned char* codeColorBuffer, ssiz
     }
 }
 
+// HALTING_* params are determined using expected acceleration of gravity over some timescale.  
+// This is a HACK for particles that bounce in a 1.0 gravitational field and should eventually be made more universal.
+const float HALTING_PARTICLE_PERIOD = 0.0167f;  // ~1/60th of a second
+const float HALTING_PARTICLE_SPEED = 9.8 * HALTING_PARTICLE_PERIOD / (float)(TREE_SCALE);
+
+void Particle::applyHardCollision(const CollisionInfo& collisionInfo) {
+    //
+    //  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.
+    //
+    //  if elasticity = 0.0, collision is inelastic (vel normal to collision is lost)
+    //  if elasticity = 1.0, collision is 100% elastic.
+    //
+    glm::vec3 position = getPosition();
+    glm::vec3 velocity = getVelocity();
+
+    const float EPSILON = 0.0f;
+    glm::vec3 relativeVelocity = collisionInfo._addedVelocity - velocity;
+    float velocityDotPenetration = glm::dot(relativeVelocity, collisionInfo._penetration);
+    if (velocityDotPenetration < EPSILON) {
+        // particle is moving into collision surface
+        //
+        // TODO: do something smarter here by comparing the mass of the particle vs that of the other thing 
+        // (other's mass could be stored in the Collision Info).  The smaller mass should surrender more 
+        // position offset and should slave more to the other's velocity in the static-friction case.
+        position -= collisionInfo._penetration;
+
+        if (glm::length(relativeVelocity) < HALTING_PARTICLE_SPEED) {
+            // static friction kicks in and particle moves with colliding object
+            velocity = collisionInfo._addedVelocity;
+        } else {
+            glm::vec3 direction = glm::normalize(collisionInfo._penetration);
+            velocity += glm::dot(relativeVelocity, direction) * (1.0f + collisionInfo._elasticity) * direction;    // dynamic reflection
+            velocity += glm::clamp(collisionInfo._damping, 0.0f, 1.0f) * (relativeVelocity - glm::dot(relativeVelocity, direction) * direction);   // dynamic friction
+        }
+    }
+
+    // change the local particle too...
+    setPosition(position);
+    setVelocity(velocity);
+}
+
 // MIN_VALID_SPEED is obtained by computing speed gained at one gravity during the shortest expected frame period
+// This is a HACK for particles that bounce in a 1.0 gravitational field and should eventually be made more universal.
 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);
 

libraries/particles/src/Particle.h

@@ -16,6 +16,7 @@
 #include <QtScript/QScriptEngine>
 #include <QtCore/QObject>
 
+#include <CollisionInfo.h>
 #include <SharedUtil.h>
 #include <OctreePacketData.h>
 
@@ -240,6 +241,8 @@ public:
 
     static void adjustEditPacketForClockSkew(unsigned char* codeColorBuffer, ssize_t length, int clockSkew);
 
+    void applyHardCollision(const CollisionInfo& collisionInfo);
+
     void update(const uint64_t& now);
     void collisionWithParticle(Particle* other);
     void collisionWithVoxel(VoxelDetail* voxel);

libraries/particles/src/ParticleCollisionSystem.cpp

@@ -73,6 +73,8 @@ void ParticleCollisionSystem::updateCollisionWithVoxels(Particle* particle) {
     const float DAMPING = 0.05f;
     const float COLLISION_FREQUENCY = 0.5f;
     CollisionInfo collisionInfo;
+    collisionInfo._damping = DAMPING;
+    collisionInfo._elasticity = ELASTICITY;
     VoxelDetail* voxelDetails = NULL;
     if (_voxels->findSpherePenetration(center, radius, collisionInfo._penetration, (void**)&voxelDetails)) {
 
@@ -81,7 +83,8 @@ void ParticleCollisionSystem::updateCollisionWithVoxels(Particle* particle) {
 
         updateCollisionSound(particle, collisionInfo._penetration, COLLISION_FREQUENCY);
         collisionInfo._penetration /= (float)(TREE_SCALE);
-        applyHardCollision(particle, ELASTICITY, DAMPING, collisionInfo);
+        particle->applyHardCollision(collisionInfo);
+        queueParticlePropertiesUpdate(particle);
 
         delete voxelDetails; // cleanup returned details
     }
@@ -161,6 +164,8 @@ void ParticleCollisionSystem::updateCollisionWithAvatars(Particle* particle) {
     if (_selfAvatar) {
         AvatarData* avatar = (AvatarData*)_selfAvatar;
         CollisionInfo collisionInfo;
+        collisionInfo._damping = DAMPING;
+        collisionInfo._elasticity = ELASTICITY;
         if (avatar->findSphereCollision(center, radius, collisionInfo)) {
             collisionInfo._addedVelocity /= (float)(TREE_SCALE);
             glm::vec3 relativeVelocity = collisionInfo._addedVelocity - particle->getVelocity();
@@ -185,7 +190,8 @@ void ParticleCollisionSystem::updateCollisionWithAvatars(Particle* particle) {
 
                 updateCollisionSound(particle, collisionInfo._penetration, COLLISION_FREQUENCY);
                 collisionInfo._penetration /= (float)(TREE_SCALE);
-                applyHardCollision(particle, elasticity, damping, collisionInfo);
+                particle->applyHardCollision(collisionInfo);
+                queueParticlePropertiesUpdate(particle);
             }
         }
     }
@@ -224,51 +230,14 @@ void ParticleCollisionSystem::updateCollisionWithAvatars(Particle* particle) {
 //    }
 }
 
-// TODO: convert applyHardCollision() to take a CollisionInfo& instead of penetration + addedVelocity
+void ParticleCollisionSystem::queueParticlePropertiesUpdate(Particle* particle) {
-void ParticleCollisionSystem::applyHardCollision(Particle* particle, float elasticity, float damping, const CollisionInfo& collisionInfo) {
+    // queue the result for sending to the particle server
-    //
-    //  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.
-    //
-    //  if elasticity = 0.0, collision is inelastic (vel normal to collision is lost)
-    //  if elasticity = 1.0, collision is 100% elastic.
-    //
-    glm::vec3 position = particle->getPosition();
-    glm::vec3 velocity = particle->getVelocity();
-
-    const float EPSILON = 0.0f;
-    glm::vec3 relativeVelocity = collisionInfo._addedVelocity - velocity;
-    float velocityDotPenetration = glm::dot(relativeVelocity, collisionInfo._penetration);
-    if (velocityDotPenetration < EPSILON) {
-        // particle is moving into collision surface
-        position -= collisionInfo._penetration;
-
-        if (glm::length(relativeVelocity) < HALTING_SPEED) {
-            // static friction kicks in and particle moves with colliding object
-            velocity = collisionInfo._addedVelocity;
-        } else {
-            glm::vec3 direction = glm::normalize(collisionInfo._penetration);
-            velocity += glm::dot(relativeVelocity, direction) * (1.0f + elasticity) * direction;    // dynamic reflection
-            velocity += glm::clamp(damping, 0.0f, 1.0f) * (relativeVelocity - glm::dot(relativeVelocity, direction) * direction);   // dynamic friction
-        }
-    }
-    const bool wantDebug = false;
-    if (wantDebug) {
-        printf("ParticleCollisionSystem::applyHardCollision() particle id:%d new velocity:%f,%f,%f inHand:%s\n",
-            particle->getID(), velocity.x, velocity.y, velocity.z, debug::valueOf(particle->getInHand()));
-    }
-
-    // send off the result to the particle server
     ParticleProperties properties;
     ParticleID particleID(particle->getID());
     properties.copyFromParticle(*particle);
-    properties.setPosition(position * (float)TREE_SCALE);
+    properties.setPosition(particle->getPosition() * (float)TREE_SCALE);
-    properties.setVelocity(velocity * (float)TREE_SCALE);
+    properties.setVelocity(particle->getVelocity() * (float)TREE_SCALE);
     _packetSender->queueParticleEditMessage(PACKET_TYPE_PARTICLE_ADD_OR_EDIT, particleID, properties);
-
-    // change the local particle too...
-    particle->setPosition(position);
-    particle->setVelocity(velocity);
 }
 
 

libraries/particles/src/ParticleCollisionSystem.h

@@ -47,7 +47,7 @@ public:
     void updateCollisionWithVoxels(Particle* particle);
     void updateCollisionWithParticles(Particle* particle);
     void updateCollisionWithAvatars(Particle* particle);
-    void applyHardCollision(Particle* particle, float elasticity, float damping, const CollisionInfo& collisionInfo);
+    void queueParticlePropertiesUpdate(Particle* particle);
     void updateCollisionSound(Particle* particle, const glm::vec3 &penetration, float frequency);
 
 private:

libraries/shared/src/CollisionInfo.h

@@ -13,11 +13,19 @@
 
 class CollisionInfo {
 public:
-    CollisionInfo() : _penetration(0.f), _addedVelocity(0.f) { }
+    CollisionInfo() 
+        : _damping(0.f),
+        _elasticity(1.f),
+        _penetration(0.f), 
+        _addedVelocity(0.f) { 
+        }
+
     ~CollisionInfo() {}
 
     //glm::vec3 _point;
     //glm::vec3 _normal;
+    float _damping;
+    float _elasticity;
     glm::vec3 _penetration; // depth that bodyA is penetrates bodyB
     glm::vec3 _addedVelocity;
 };