#include "animation.h"
#include <math.h>
#include <stdlib.h> // RAND_MAX

using namespace qglviewer;
using namespace std;

///////////////////////   V i e w e r  ///////////////////////
void Viewer::init()
{
  restoreFromFile();
  glDisable(GL_LIGHTING);
  nbPart_ = 2000;
  particle_ = new Particle[nbPart_];	
  glPointSize(3.0);
  setDrawGrid();
  help();
  startAnimation();
}

void Viewer::draw()
{
  glBegin(GL_POINTS);
  for (int i=0; i<nbPart_; i++)
    particle_[i].draw();
  glEnd();
}

void Viewer::animate()
{
  for (int i=0; i<nbPart_; i++)
    particle_[i].animate();
}

QString Viewer::helpString() const
{
  QString text("<h2>A n i m a t i o n</h2>");
  text += "Use the <i>animate()</i> function to implement the animation part of your ";
  text += "application. Once the animation is started, <i>animate()</i> and <i>draw()</i> ";
  text += "are called in an infinite loop, at a frequency that can be fixed.<br>";
  text += "Press <b>Return</b> to start/stop the animation.";
  return text;
}

///////////////////////   P a r t i c l e   ///////////////////////////////

Particle::Particle()
{
  init();
}

void Particle::animate()
{
  speed_.z -= 0.05;
  pos_     += 0.1 * speed_;

  if (pos_.z < 0.0)
    {
      speed_.z = -0.8*speed_.z;
      pos_.z = 0.0;
    }

  if (++age_ == ageMax_)
    init();
}

void Particle::draw()
{
  glColor3f(age_/(float)ageMax_, age_/(float)ageMax_, 1.0);
  glVertex3fv(pos_.address());
}


void Particle::init()
{
  pos_ = Vec(0.0, 0.0, 0.0);
  float angle = 2.0 * M_PI * rand() / RAND_MAX;
  float norm  = 0.04 * rand() / RAND_MAX;
  speed_ = Vec(norm*cos(angle), norm*sin(angle), rand() / static_cast<float>(RAND_MAX) );
  age_ = 0;
  ageMax_ = 50 + static_cast<int>(100.0 * rand() / RAND_MAX);
}