////  ParticleSystem.h//  hifi////  Created by Jeffrey on July 10, 2013// #ifndef hifi_ParticleSystem_h#define hifi_ParticleSystem_h #include <glm/gtc/quaternion.hpp> const int  MAX_PARTICLES            = 5000;const int  MAX_EMITTERS             = 1000;const int  NUM_PARTICLE_LIFE_STAGES = 4;  // each equal time-division of the particle's life can have different attributesconst bool SHOW_VELOCITY_TAILS      = false; enum ParticleRenderStyle{    PARTICLE_RENDER_STYLE_SPHERE = 0,    PARTICLE_RENDER_STYLE_BILLBOARD,    PARTICLE_RENDER_STYLE_RIBBON,    NUM_PARTICLE_RENDER_STYLES}; class ParticleSystem {public:     struct ParticleAttributes {        float     radius;                   // radius of the particle        glm::vec4 color;                    // color (rgba) of the particle        float     bounce;                   // how much reflection when the particle collides with floor/ground        float     gravity;                  // force opposite of up direction         float     airFriction;              // continual dampening of velocity        float     jitter;                   // random forces on velocity        float     emitterAttraction;        // an attraction to the emitter position        float     tornadoForce;             // force perpendicular to direction axis        float     neighborAttraction;       // causes particle to be pulled towards next particle in list        float     neighborRepulsion;        // causes particle to be repelled by previous particle in list        bool      usingCollisionSphere;     // set to true to allow collision with a sphere        glm::vec3 collisionSpherePosition;  // position of the collision sphere        float     collisionSphereRadius;    // radius of the collision sphere    };       // public methods...    ParticleSystem();        int  addEmitter(); // add (create new) emitter and get its unique id    void emitNow(int emitterIndex);    void simulate(float deltaTime);    void killAllParticles();    void render();        void setUpDirection(glm::vec3 upDirection) {_upDirection = upDirection;} // tell particle system which direction is up    void setParticleAttributes        (int emitterIndex, ParticleAttributes attributes); // set attributes for whole life of particles    void setParticleAttributes        (int emitterIndex, int lifeStage, ParticleAttributes attributes); // set attributes for this life stage of particles    void setEmitterPosition           (int emitterIndex, glm::vec3           position    ) {_emitter[emitterIndex].position            = position;    }     void setEmitterParticleResolution (int emitterIndex, int                 resolution  ) {_emitter[emitterIndex].particleResolution  = resolution;  }     void setEmitterDirection          (int emitterIndex, glm::vec3           direction   ) {_emitter[emitterIndex].direction           = direction;   }     void setShowingEmitter            (int emitterIndex, bool                showing     ) {_emitter[emitterIndex].visible             = showing;     }      void setEmitterParticleLifespan   (int emitterIndex, float               lifespan    ) {_emitter[emitterIndex].particleLifespan    = lifespan;    }    void setParticleRenderStyle       (int emitterIndex, ParticleRenderStyle renderStyle ) {_emitter[emitterIndex].particleRenderStyle = renderStyle; }    void setEmitterThrust             (int emitterIndex, float               thrust      ) {_emitter[emitterIndex].thrust              = thrust;      }    void setEmitterRate               (int emitterIndex, float               rate        ) {_emitter[emitterIndex].rate                = rate;        }    void setShowingEmitterBaseParticle(int emitterIndex, bool                showing     ) {_emitter[emitterIndex].showingBaseParticle = showing;     } private:        struct Particle {        bool      alive;            // is the particle active?        glm::vec3 position;         // position        glm::vec3 velocity;         // velocity        glm::vec4 color;            // color (rgba)        float     age;              // age in seconds        float     radius;           // radius        int       emitterIndex;     // which emitter created this particle?        int       previousParticle; // the last particle that this particle's emitter emitted;    };             struct Emitter {        glm::vec3 position;            // the position of the emitter in world coordinates        glm::vec3 direction;           // a normalized vector used as an axis for particle emission and other effects        bool      visible;             // whether or not a line is shown indicating the emitter (indicating its direction)        float     particleLifespan;    // how long the particle shall live, in seconds        int       particleResolution;  // for sphere-based particles        float     thrust;              // the initial velocity upon emitting along the emitter direction         float     rate;                // currently, how many particles emitted during a simulation time step        bool      showingBaseParticle; // if true, a copy of particle 0 is shown on the emitter position        int       currentParticle;     // the index of the most recently-emitted particle        ParticleAttributes particleAttributes[NUM_PARTICLE_LIFE_STAGES]; // the attributes of particles emitted from this emitter        ParticleRenderStyle particleRenderStyle;    };     glm::vec3 _upDirection;    Emitter   _emitter[MAX_EMITTERS];    Particle  _particle[MAX_PARTICLES];    int       _numParticles;    int       _numEmitters;        // private methods    void updateParticle(int index, float deltaTime);    void createParticle(int e, glm::vec3 velocity);    void killParticle(int p);    void renderEmitter(int emitterIndex, float size);    void renderParticle(int p);}; #endif