////  ParticleSystem.cpp//  hifi////  Created by Jeffrey on July 10, 2013// #include <glm/glm.hpp>#include "InterfaceConfig.h"#include <SharedUtil.h> #include "ParticleSystem.h" ParticleSystem::ParticleSystem() {     _numberOfParticles = 1500;    assert(_numberOfParticles <= MAX_PARTICLES);     _bounce             = 0.9f;    _timer              = 0.0f;    _airFriction        = 6.0f;    _jitter             = 0.1f;    _homeAttraction     = 0.0f;    _tornadoForce       = 0.0f;    _neighborAttraction = 0.02f;    _neighborRepulsion  = 0.9f;    _tornadoAxis        = glm::normalize(glm::vec3(0.1f, 1.0f, 0.1f));    _home               = glm::vec3(5.0f, 0.5f, 5.0f);        _TEST_bigSphereRadius = 0.5f;    _TEST_bigSpherePosition = glm::vec3( 5.0f, _TEST_bigSphereRadius, 5.0f);     for (unsigned int p = 0; p < _numberOfParticles; p++) {        _particle[p].position = _home;        _particle[p].velocity = glm::vec3(0.0f, 0.0f, 0.0f);                float red   = 0.5f + 0.5f * sinf(((float)p / (float)_numberOfParticles) * 3.141592 * 2.0f);        float green = 0.3f + 0.3f * sinf(((float)p / (float)_numberOfParticles) * 3.141592 * 2.0f);        float blue  = 0.2f - 0.2f * sinf(((float)p / (float)_numberOfParticles) * 3.141592 * 2.0f);                _particle[p].color    = glm::vec3(red, green, blue);        _particle[p].age      = 0;        _particle[p].radius   = 0.01f;    }} void ParticleSystem::simulate(float deltaTime) {     _timer += deltaTime;     _gravity            = 0.01f  + 0.01f  * sinf( _timer * 0.52f );    _airFriction        = 3.0f   + 2.0f   * sinf( _timer * 0.32f );    _jitter             = 0.05f  + 0.05f  * sinf( _timer * 0.42f );    _homeAttraction     = 0.01f  + 0.01f  * cosf( _timer * 0.6f  );    _tornadoForce       = 0.0f   + 0.03f  * sinf( _timer * 0.7f  );    _neighborAttraction = 0.1f   + 0.1f   * cosf( _timer * 0.8f  );    _neighborRepulsion  = 0.4f   + 0.3f   * sinf( _timer * 0.4f  );     _tornadoAxis = glm::vec3    (        0.0f + 0.5f * sinf( _timer * 0.55f ),        1.0f,        0.0f + 0.5f * cosf( _timer * 0.75f )    );     for (unsigned int p = 0; p < _numberOfParticles; p++) {         // apply random jitter        _particle[p].velocity +=         glm::vec3        (            -_jitter * ONE_HALF + _jitter * randFloat(),             -_jitter * ONE_HALF + _jitter * randFloat(),             -_jitter * ONE_HALF + _jitter * randFloat()        ) * deltaTime;                        // apply attraction to home position        glm::vec3 vectorToHome = _home - _particle[p].position;        _particle[p].velocity += vectorToHome * _homeAttraction * deltaTime;                // apply neighbor attraction        int neighbor = p + 1;        if (neighbor == _numberOfParticles ) {            neighbor = 0;        }        glm::vec3 vectorToNeighbor = _particle[p].position - _particle[neighbor].position;                _particle[p].velocity -= vectorToNeighbor * _neighborAttraction * deltaTime;         float distanceToNeighbor = glm::length(vectorToNeighbor);        if (distanceToNeighbor > 0.0f) {            _particle[neighbor].velocity += (vectorToNeighbor / ( 1.0f + distanceToNeighbor * distanceToNeighbor)) * _neighborRepulsion * deltaTime;        }                // apply tornado force        glm::vec3 tornadoDirection = glm::cross(vectorToHome, _tornadoAxis);        _particle[p].velocity += tornadoDirection * _tornadoForce * deltaTime;         // apply air friction        float drag = 1.0 - _airFriction * deltaTime;        if (drag < 0.0f) {            _particle[p].velocity = glm::vec3(0.0f, 0.0f, 0.0f);        } else {            _particle[p].velocity *= drag;        }                // apply gravity        _particle[p].velocity.y -= _gravity * deltaTime;                // update position by velocity        _particle[p].position += _particle[p].velocity;                // collision with ground        if (_particle[p].position.y < _particle[p].radius) {            _particle[p].position.y = _particle[p].radius;                        if (_particle[p].velocity.y < 0.0f) {                _particle[p].velocity.y *= -_bounce;            }        }                // collision with sphere        glm::vec3 vectorToSphereCenter = _TEST_bigSpherePosition - _particle[p].position;        float distanceToSphereCenter = glm::length(vectorToSphereCenter);        float combinedRadius = _TEST_bigSphereRadius + _particle[p].radius;        if (distanceToSphereCenter < combinedRadius) {                    if (distanceToSphereCenter > 0.0f){                glm::vec3 directionToSphereCenter = vectorToSphereCenter / distanceToSphereCenter;                _particle[p].position = _TEST_bigSpherePosition - directionToSphereCenter * combinedRadius;                            _particle[p].velocity.y += 0.005f;                        }        }    }}   void ParticleSystem::render() {     for (unsigned int p = 0; p < _numberOfParticles; p++) {        glColor3f(_particle[p].color.x, _particle[p].color.y, _particle[p].color.z);        glPushMatrix();        glTranslatef(_particle[p].position.x, _particle[p].position.y, _particle[p].position.z);        glutSolidSphere(_particle[p].radius, 6, 6);        glPopMatrix();            // render velocity lines        glColor4f( _particle[p].color.x, _particle[p].color.y, _particle[p].color.z, 0.5f);        glm::vec3 end = _particle[p].position - _particle[p].velocity * 2.0f;        glBegin(GL_LINES);        glVertex3f(_particle[p].position.x, _particle[p].position.y, _particle[p].position.z);        glVertex3f(end.x, end.y, end.z);                glEnd();            }}