////  Balls.cpp//  hifi////  Created by Philip on 4/25/13.////  A cloud of spring-mass spheres to simulate the avatar body/skin.  Each ball//  connects to as many as 4 neighbors, and executes motion according to a damped//  spring, while responding physically to other avatars.   //   #include "Balls.h" Balls::Balls(int numberOfBalls) {    _numberOfBalls = numberOfBalls;    _balls = new Ball[_numberOfBalls];    for (unsigned int i = 0; i < _numberOfBalls; ++i) {        _balls[i].position = glm::vec3(1.0 + randFloat() * 0.5,                                       0.5 + randFloat() * 0.5,                                       1.0 + randFloat() * 0.5);        _balls[i].radius = 0.02 + randFloat() * 0.06;        for (unsigned int j = 0; j < NUMBER_SPRINGS; ++j) {            _balls[i].links[j] = rand() % (numberOfBalls + 1);            if (_balls[i].links[j]-1 == i) { _balls[i].links[j] = 0; }            _balls[i].springLength[j] = 0.5;         }    }} const bool RENDER_SPRINGS = true; void Balls::render() {        //  Render Balls    NOTE:  This needs to become something other that GlutSpheres!    glColor3f(0.62,0.74,0.91);    for (unsigned int i = 0; i < _numberOfBalls; ++i) {        glPushMatrix();        glTranslatef(_balls[i].position.x, _balls[i].position.y, _balls[i].position.z);        glutSolidSphere(_balls[i].radius, 15, 15);        glPopMatrix();    }        //  Render springs    if (RENDER_SPRINGS) {        glColor3f(0.74, 0.91, 0.62);        for (unsigned int i = 0; i < _numberOfBalls; ++i) {            glBegin(GL_LINES);            for (unsigned int j = 0; j < NUMBER_SPRINGS; ++j) {                if(_balls[i].links[j] > 0) {                    glVertex3f(_balls[i].position.x,                               _balls[i].position.y,                               _balls[i].position.z);                    glVertex3f(_balls[_balls[i].links[j]-1].position.x,                               _balls[_balls[i].links[j]-1].position.y,                               _balls[_balls[i].links[j]-1].position.z);                }            }            glEnd();        }    }     } const float CONSTANT_VELOCITY_DAMPING = 1.0f;const float NOISE_SCALE = 0.00;const float SPRING_FORCE = 1.0;const float SPRING_DAMPING = 1.0; void Balls::simulate(float deltaTime) {    for (unsigned int i = 0; i < _numberOfBalls; ++i) {                // Move particles        _balls[i].position += _balls[i].velocity * deltaTime;                // Drag: decay velocity        _balls[i].velocity *= (1.f - CONSTANT_VELOCITY_DAMPING * deltaTime);                // Add noise        _balls[i].velocity += glm::vec3((randFloat() - 0.5) * NOISE_SCALE,                                        (randFloat() - 0.5) * NOISE_SCALE,                                        (randFloat() - 0.5) * NOISE_SCALE);                // Spring Force                        for (unsigned int j = 0; j < NUMBER_SPRINGS; ++j) {            if(_balls[i].links[j] > 0) {                float separation = glm::distance(_balls[i].position,                                                _balls[_balls[i].links[j]-1].position);                _balls[i].velocity += glm::normalize(_balls[i].position -                                                   _balls[_balls[i].links[j]-1].position) *                                        deltaTime *                                        SPRING_FORCE *                                        (_balls[i].springLength[j] - separation);                                //_balls[i].velocity *= (1.f - SPRING_DAMPING*deltaTime);             }        }                               }}